feat(packages): add commons package

This is an import of 166ca8da12
with some changes to make it fit into the mono repo.
- TypedEventEmitter has been replaced with EventEmitter2 because EventEmitter2 is faster and TypedEventEmitter had some troubles with the new way of compiling.
- tsc-esm has been replaced with microbundle. The problems that lib0 doesn't export its types correctly has been solved using yarn patch.

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

commons/.eslintrc.cjs

@@ -0,0 +1,40 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+module.exports = {
+    "parser": "@typescript-eslint/parser",
+    "parserOptions": {
+        "project": [
+            "./tsconfig-eslint.json"
+        ]
+    },
+    "plugins": [
+        "@typescript-eslint",
+        "jest",
+        "prettier"
+    ],
+    "env": {
+        "jest": true,
+        "jest/globals": true
+    },
+    "extends": [
+        "eslint:recommended",
+        "plugin:@typescript-eslint/eslint-recommended",
+        "plugin:@typescript-eslint/recommended-requiring-type-checking",
+        "plugin:@typescript-eslint/recommended",
+        "prettier"
+    ],
+    "rules": {
+        "prettier/prettier": ["error",
+            require('./.prettierrc.json')
+        ],
+        "jest/no-disabled-tests": "warn",
+        "jest/no-focused-tests": "error",
+        "jest/no-identical-title": "error",
+        "jest/prefer-to-have-length": "warn",
+        "jest/valid-expect": "error"
+    }
+}