feat: create flowtype config

Author: G-Rath

flowtype.js

@@ -0,0 +1,38 @@
+module.exports = {
+  parser: 'babel-eslint',
+  plugins: ['flowtype'],
+  extends: ['plugin:flowtype/recommended', 'prettier/flowtype'],
+  rules: {
+    'flowtype/array-style-complex-type': ['error', 'verbose'],
+    'flowtype/array-style-simple-type': ['error', 'shorthand'],
+    'flowtype/arrow-parens': ['error', 'as-needed'],
+    'flowtype/define-flow-type': 'error',
+    'flowtype/newline-after-flow-annotation': 'error',
+    'flowtype/no-dupe-keys': 'error',
+    'flowtype/no-existential-type': 'error',
+    'flowtype/no-flow-fix-me-comments': 'error',
+    'flowtype/no-mixed': 'warn',
+    'flowtype/no-primitive-constructor-types': 'error',
+    'flowtype/no-unused-expressions': 'error',
+    'flowtype/no-weak-types': 'error',
+    'flowtype/require-compound-type-alias': 'warn',
+    'flowtype/require-exact-type': 'warn',
+    'flowtype/require-indexer-name': ['error', 'always'],
+    'flowtype/require-inexact-type': 'error',
+    'flowtype/require-parameter-type': 'error',
+    'flowtype/require-readonly-react-props': 'error',
+    'flowtype/require-return-type': [
+      'warn',
+      'always',
+      { excludeArrowFunctions: true }
+    ],
+    'flowtype/require-types-at-top': 'warn',
+    'flowtype/require-valid-file-annotation': [
+      'error',
+      'always',
+      { annotationStyle: 'line', strict: true }
+    ],
+    'flowtype/spread-exact-type': 'error',
+    'flowtype/type-import-style': ['error', 'declaration']
+  }
+};

package-lock.json

@@ -10,6 +10,7 @@
   "license": "ISC",
   "author": "Gareth Jones",
   "files": [
+    "flowtype.js",
     "index.js",
     "jest.js"
   ],
@@ -55,8 +56,10 @@
     "@typescript-eslint/eslint-plugin": "^2.16.0",
     "@typescript-eslint/experimental-utils": "^2.16.0",
     "@typescript-eslint/parser": "^2.16.0",
+    "babel-eslint": "^10.0.3",
     "eslint": "^6.8.0",
     "eslint-plugin-eslint-comments": "^3.1.2",
+    "eslint-plugin-flowtype": "^4.6.0",
     "eslint-plugin-jest": "^23.4.0",
     "eslint-plugin-local": "^1.0.0",
     "eslint-plugin-prettier": "^3.1.2",