feat: add powershell (#442)

- [x] I ran `make setup && make` to update the generated code after
editing a `.atd` file
- [x] I made sure we're still backward compatible with old versions of
the CLI.
For example, the Semgrep backend need to still be able to *consume* data
	  generated by Semgrep 1.50.0.
See
https://atd.readthedocs.io/en/latest/atdgen-tutorial.html#smooth-protocol-upgrades
	  Note that the types related to the semgrep-core JSON output or the
	  semgrep-core RPC do not need to be backward compatible!
- [x] Any accompanying changes in `semgrep-proprietary` are approved and
ready to merge once this PR is merged

Author: brandonspark

Language.ml

@@ -30,6 +30,7 @@ type t =
 | Move_on_aptos
 | Ocaml
 | Php
+| Powershell
 | Promql
 | Protobuf
 | Python2
@@ -456,6 +457,19 @@ let list = [
   shebangs = [{|php|}];
   tags = [];
 };
+{
+  id = Powershell;
+  id_string = "powershell";
+  name = "Powershell";
+  keys = [{|powershell|}];
+  exts = [{|.ps1|}];
+  maturity = Alpha;
+  example_ext = None;
+  excluded_exts = [];
+  reverse_exts = None;
+  shebangs = [];
+  tags = [];
+};
 {
   id = Promql;
   id_string = "promql";

Language.mli

@@ -30,6 +30,7 @@ type t =
 | Move_on_aptos
 | Ocaml
 | Php
+| Powershell
 | Promql
 | Protobuf
 | Python2

generate.py

@@ -467,6 +467,14 @@ def to_json(self):
         maturity=Maturity.GA,
         shebangs=["php"]
     ),
+    Language(
+        comment="",
+        id_="powershell",
+        name="Powershell",
+        keys=["powershell"],
+        exts=[".ps1"],
+        maturity=Maturity.ALPHA,
+    ),
     Language(
         comment="",
         id_="promql",

lang.json

@@ -549,6 +549,23 @@
     "is_target_language": true,
     "tags": []
   },
+  {
+    "id": "powershell",
+    "name": "Powershell",
+    "keys": [
+      "powershell"
+    ],
+    "maturity": "alpha",
+    "exts": [
+      ".ps1"
+    ],
+    "example_ext": null,
+    "excluded_exts": [],
+    "reverse_exts": null,
+    "shebangs": [],
+    "is_target_language": true,
+    "tags": []
+  },
   {
     "id": "promql",
     "name": "Prometheus Query Language",