Combine ESLint configurations

Instead of having different ESLint configuration files in each
directory which don't seem to inherit the configuration correctly, this
will add `overrides` in the root file.

extensions/ql-vscode/tsconfig.lint.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./tsconfig.json",
+  "include": ["src/**/*.ts", "**/.eslintrc.js", "jest.config.js"]
+}