Implement TOML serdes std library (#79)

Derived from [bjcscat's JSON serdes std
library](#67)

Closes #64

This PR adds TOML serialization and deserialization to Lute, enabling
migration from tools that use TOML configuration files.
Features included:

- Key-value pairs (string, number, boolean)
- Nested tables ([section])
- Array-of-tables ([[array]])
- Inline tables ({ key = value })

Buffer-based serialization for performance

Future improvements: Datetime support.

---------

Co-authored-by: ariel <aweiss@hey.com>

Author: unfetchable

batteries/toml.luau

@@ -0,0 +1,171 @@
+local toml = {}
+
+-- serialization
+type SerializerState = {
+	buf: buffer,
+	cursor: number,
+}
+
+local function serializeValue(value: string | number)
+	if typeof(value) == "string" then
+		value = string.gsub(value, '\\', '\\\\')
+		value = string.gsub(value, '\n', '\\n')
+		value = string.gsub(value, '\t', '\\t')
+		return "\"" .. value .. "\""
+	elseif value == math.huge then
+		return "inf"
+	elseif value == -math.huge then
+		return "-inf"
+	elseif value ~= value then
+		return "nan"
+	else
+		return tostring(value)
+	end
+end
+
+local function hasNestedTables(tbl: {})
+	for _, v in tbl do
+		if typeof(v) == "table" and next(v) ~= nil then
+			return true
+		end
+	end
+	return false
+end
+
+local function tableToToml(tbl: {}, parent: string)
+	local result = ""
+	local subTables = {}
+	local hasDirectValues = false
+
+	for k, v in tbl do
+		if typeof(v) == "table" and next(v) ~= nil then
+			if #v > 0 then
+				for _, entry in v do
+					result ..= "\n[[" .. (parent and parent .. "." or "") .. k .. "]]\n"
+					result ..=  tableToToml(entry, nil)
+				end
+			else
+				subTables[k] = v
+			end
+		else
+			hasDirectValues = true
+			result ..= k .. " = " .. serializeValue(v) .. "\n"
+		end
+	end
+
+	for k, v in subTables do
+		local key = parent and (parent .. "." .. k) or k
+		
+		if hasNestedTables(v) == true then
+			result ..= tableToToml(v, key)
+			continue
+		end
+
+		if hasDirectValues or parent then
+			result ..= "\n[" .. key .. "]\n"
+		end
+
+		result ..= tableToToml(v, key)
+	end
+
+	return result
+end
+
+
+local function serialize(tbl: {}): string
+	return tableToToml(tbl, nil)
+end
+
+-- deserialization
+type DeserializerState = {
+	buf: string,
+	cursor: number,
+}
+
+local function skipWhitespace(state: DeserializerState)
+	local pos = state.cursor
+	while pos <= string.len(state.buf) and string.match(string.sub(state.buf, pos, pos), "%s") do
+		pos += 1
+	end
+	state.cursor = pos
+end
+
+local function readLine(state: DeserializerState)
+	local nextLine = string.find(state.buf, "\n", state.cursor) or string.len(state.buf) + 1
+	local line = string.sub(state.buf, state.cursor, nextLine - 1)
+	state.cursor = nextLine + 1
+	return line
+end
+
+local function deserialize(input: string)
+	local state: DeserializerState = {
+		buf = input,
+		cursor = 1,
+	}
+	local result = {}
+	local currentTable = result
+	local arrayTables = {}
+
+	while state.cursor <= string.len(state.buf) do
+		skipWhitespace(state)
+		local line = readLine(state)
+
+		if line == "" or string.sub(line, 1, 1) == "#" then
+			continue
+		end
+
+		if string.match(line, "^%[%[(.-)%]%]$") then
+			local tableName = string.match(line, "^%[%[(.-)%]%]$")
+			arrayTables[tableName] = arrayTables[tableName] or {}
+
+			local newEntry = {}
+			table.insert(arrayTables[tableName], newEntry)
+
+			result[tableName] = arrayTables[tableName]
+			currentTable = newEntry
+		elseif string.match(line, "^%[(.-)%]$") then
+			local tablePath = string.match(line, "^%[(.-)%]$")
+			local parent = result
+
+			for section in string.gmatch(tablePath, "([^.]+)") do
+				if not parent[section] then parent[section] = {} end
+				parent = parent[section]
+			end
+
+			currentTable = parent
+		elseif string.match(line, "^(.-)%s*=%s*(.-)$") then
+			local key, value = string.match(line, "^(.-)%s*=%s*(.-)$")
+			key = string.match(key, "^%s*(.-)%s*$")
+			value = string.match(value, "^%s*(.-)%s*$")
+
+			if string.match(value, '^"(.*)"$') or string.match(value, "^'(.*)'$") then
+				value = string.sub(value, 2, -2)
+				value = string.gsub(value, '\\\\', '\\')
+				value = string.gsub(value, '\\n', '\n')
+				value = string.gsub(value, '\\t', '\t')
+			elseif tonumber(value) then
+				value = tonumber(value)
+			elseif value == "true" then
+				value = true
+			elseif value == "false" then
+				value = false
+			elseif value == "inf" or value == "+inf" then
+				value = math.huge
+			elseif value == "-inf" then
+				value = -math.huge
+			elseif value == "nan" then
+				value = 0/0
+			end
+
+			currentTable[key] = value
+		end
+	end
+
+	return result
+end
+
+-- user-facing
+toml.serialize = serialize
+toml.deserialize = deserialize
+
+return toml

examples/toml.luau

@@ -0,0 +1,30 @@
+local toml = require("@batteries/toml")
+
+local deserialized = toml.deserialize([=[
+hello = "world"
+infinity = inf
+nan_value = nan
+escaped_string = "This is a string with a newline\ncharacter"
+
+[world]
+v1 = "hi"
+v2 = 8080
+v3 = true
+
+[[users]]
+name = "Alice"
+age = 25
+
+[[users]]
+name = "Bob"
+age = 30
+
+[people.Tom]
+age = 33
+]=])
+
+local serialized = toml.serialize(deserialized)
+
+print(serialized)
+
+print(deserialized)