web: De-duplicate TypeScript ESLint rules

Pull them to the root config, using the `overrides` feature:
https://eslint.org/docs/user-guide/configuring/configuration-files#configuration-based-on-glob-patterns

web/.eslintrc.yaml

@@ -8,3 +8,17 @@ rules:
   no-unused-vars:
     - error
     - argsIgnorePattern: ^_
+overrides:
+  # TypeScript rules.
+  - files:
+      - '*.ts'
+    parser: '@typescript-eslint/parser'
+    plugins:
+      - '@typescript-eslint'
+    extends:
+      - plugin:@typescript-eslint/recommended
+    rules:
+      '@typescript-eslint/no-non-null-assertion': 'off'
+      '@typescript-eslint/no-unused-vars':
+        - error
+        - argsIgnorePattern: ^_

web/packages/core/src/.eslintrc.yaml

@@ -1,17 +1,10 @@
 env:
   browser: true
-parser: '@typescript-eslint/parser'
 plugins:
-  - '@typescript-eslint'
   - jsdoc
 extends:
-  - plugin:@typescript-eslint/recommended
   - plugin:jsdoc/recommended
 rules:
-  '@typescript-eslint/no-non-null-assertion': 'off'
-  '@typescript-eslint/no-unused-vars':
-    - error
-    - argsIgnorePattern: ^_
   jsdoc/no-types: error
   jsdoc/require-returns-type: 'off'
   jsdoc/require-param-type: 'off'

web/packages/extension/src/.eslintrc.yaml

@@ -1,13 +1,3 @@
 env:
   browser: true
   webextensions: true
-parser: '@typescript-eslint/parser'
-plugins:
-  - '@typescript-eslint'
-extends:
-  - plugin:@typescript-eslint/recommended
-rules:
-  '@typescript-eslint/no-non-null-assertion': 'off'
-  '@typescript-eslint/no-unused-vars':
-    - error
-    - argsIgnorePattern: ^_