Disallow .only in mocha tests (#2107)

Fixes #2105



## Checklist

- [ ] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [ ] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [ ] I have not broken the cheatsheet

Author: pokey

.eslintrc.json

@@ -11,7 +11,13 @@
     "ecmaVersion": 6,
     "sourceType": "module"
   },
-  "plugins": ["@typescript-eslint", "unused-imports", "import", "unicorn"],
+  "plugins": [
+    "@typescript-eslint",
+    "unused-imports",
+    "import",
+    "unicorn",
+    "mocha"
+  ],
   "rules": {
     "import/no-relative-packages": "error",
     "@typescript-eslint/consistent-type-assertions": [
@@ -53,7 +59,9 @@
     ],
     "no-throw-literal": "warn",
     "semi": "off",
-    "unicorn/prefer-module": "error"
+    "unicorn/prefer-module": "error",
+    "mocha/no-skipped-tests": "error",
+    "mocha/no-exclusive-tests": "error"
   },
   "overrides": [
     {

package.json

@@ -36,6 +36,7 @@
     "eslint-config-prettier": "^8.8.0",
     "eslint-import-resolver-typescript": "3.5.5",
     "eslint-plugin-import": "2.28.1",
+    "eslint-plugin-mocha": "10.2.0",
     "eslint-plugin-unicorn": "49.0.0",
     "eslint-plugin-unused-imports": "^3.0.0",
     "prettier": "3.0.3",