It's smart to keep the NodeJS version pinned so we can run all build jobs
consistently.
Otherwise, we might run into some versions mismatch like below:
```
npm ERR! While resolving: @typescript-eslint/parser@2.30.0
npm ERR! Found: eslint@7.4.0
npm ERR! node_modules/eslint
npm ERR! dev eslint@"^7.4.0" from the root project
npm ERR! peer eslint@"^5.0.0 || ^6.0.0 || ^7.0.0" from @typescript-eslint/eslint-plugin@4.11.1
npm ERR! node_modules/@typescript-eslint/eslint-plugin
npm ERR! @typescript-eslint/eslint-plugin@">=2.25.0" from eslint-plugin-github@4.1.1
npm ERR! node_modules/eslint-plugin-github
npm ERR! dev eslint-plugin-github@"^4.1.1" from the root project
npm ERR! 7 more (@typescript-eslint/experimental-utils, ...)
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer eslint@"^5.0.0 || ^6.0.0" from @typescript-eslint/parser@2.30.0
npm ERR! node_modules/@typescript-eslint/parser
npm ERR! dev @typescript-eslint/parser@"^2.30.0" from the root project
npm ERR! @typescript-eslint/parser@">=2.25.0" from eslint-plugin-github@4.1.1
npm ERR! node_modules/eslint-plugin-github
npm ERR! dev eslint-plugin-github@"^4.1.1" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: eslint@6.8.0
npm ERR! node_modules/eslint
npm ERR! peer eslint@"^5.0.0 || ^6.0.0" from @typescript-eslint/parser@2.30.0
npm ERR! node_modules/@typescript-eslint/parser
npm ERR! dev @typescript-eslint/parser@"^2.30.0" from the root project
npm ERR! @typescript-eslint/parser@">=2.25.0" from eslint-plugin-github@4.1.1
npm ERR! node_modules/eslint-plugin-github
npm ERR! dev eslint-plugin-github@"^4.1.1" from the root project
```
