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.

jest.config.ts

@@ -0,0 +1,24 @@
+export default {
+  clearMocks: true,
+  moduleFileExtensions: ['js', 'ts'],
+  roots: ['<rootDir>'],
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  transform: {
+    '^.+\\.ts$': [
+      'ts-jest',
+      {
+        useESM: true,
+        diagnostics: {
+          ignoreCodes: [151002]
+        }
+      }
+    ]
+  },
+  extensionsToTreatAsEsm: ['.ts'],
+  transformIgnorePatterns: ['node_modules/(?!(@actions)/)'],
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1'
+  },
+  verbose: true
+};