Migrate to ESM and upgrade dependencies (#763)

* Migrate to ESM and upgrade dependencies

* Remove unused tsconfig.eslint.json

* bump version to 7.0.0 in package.json and package-lock.json

* Add ESM migration note to README for V7

* Remove unnecessary devDependencies: ts-node, @types/jest

* npm audit fix

* Update README with ESM migration details

Clarified migration details to ESM for action compatibility.

* Downgrade @types/node to ^24, clean up tsconfig and README.

__tests__/utils.test.ts

@@ -1,4 +1,5 @@
-import {isSelfHosted} from '../src/utils';
+import {describe, it, expect, beforeEach, afterEach} from '@jest/globals';
+import {isSelfHosted} from '../src/utils.js';
 
 describe('utils', () => {
   describe('isSelfHosted', () => {