fix(linter): produce type information for the eslint-plugin main entry point (#29855)

## Current Behavior

The `@nx/eslint-plugin` main entry point is untyped.

## Expected Behavior

The `@nx/eslint-plugin` main entry point should provide types.

## Related Issue(s)

Fixes #28448 
Fixes #29816

packages/eslint-plugin/src/index.ts

@@ -24,8 +24,7 @@ import dependencyChecks, {
 // Resolve any custom rules that might exist in the current workspace
 import { workspaceRules } from './resolve-workspace-rules';
 
-module.exports = {
+const configs = {
-  configs: {
   // eslintrc configs
   typescript,
   javascript,
@@ -39,35 +38,38 @@ module.exports = {
   // flat configs
   // Note: Using getters here to avoid importing packages `angular-eslint` statically, which can lead to errors if not installed.
   'flat/base': flatBase,
-    get ['flat/typescript']() {
+  get ['flat/typescript'](): typeof import('./flat-configs/typescript').default {
     return require('./flat-configs/typescript').default;
   },
-    get ['flat/javascript']() {
+  get ['flat/javascript'](): typeof import('./flat-configs/javascript').default {
     return require('./flat-configs/javascript').default;
   },
-    get ['flat/react']() {
+  get ['flat/react'](): typeof import('./flat-configs/react-tmp').default {
     return require('./flat-configs/react-tmp').default;
   },
-    get ['flat/react-base']() {
+  get ['flat/react-base'](): typeof import('./flat-configs/react-base').default {
     return require('./flat-configs/react-base').default;
   },
-    get ['flat/react-typescript']() {
+  get ['flat/react-typescript'](): typeof import('./flat-configs/react-typescript').default {
     return require('./flat-configs/react-typescript').default;
   },
-    get ['flat/react-jsx']() {
+  get ['flat/react-jsx'](): typeof import('./flat-configs/react-jsx').default {
     return require('./flat-configs/react-jsx').default;
   },
-    get ['flat/angular']() {
+  get ['flat/angular'](): typeof import('./flat-configs/angular').default {
     return require('./flat-configs/angular').default;
   },
-    get ['flat/angular-template']() {
+  get ['flat/angular-template'](): typeof import('./flat-configs/angular-template').default {
     return require('./flat-configs/angular-template').default;
   },
-  },
+};
-  rules: {
+
+const rules = {
   [enforceModuleBoundariesRuleName]: enforceModuleBoundaries,
   [nxPluginChecksRuleName]: nxPluginChecksRule,
   [dependencyChecksRuleName]: dependencyChecks,
   ...workspaceRules,
-  },
 };
+
+export default { configs, rules };
+export { configs, rules };