Fix eslint and type errors in frontend package

[MSzalowski]

Due to the introduction of #511 eslint and tsc throws errors.

Result of lint execution:

✖ 672 problems (644 errors, 28 warnings)
  6 errors and 0 warnings potentially fixable with the `--fix` option.

Result of tsc execution:

Found 41 errors in 10 files.

DoD

All of the above should return no errors.

[pmbinapps]

OK NOW - There are no errors.

Still some warnings that notifies users of the deprecation of Node.js 16 actions in GitHub actions. It advises updating to Node.js 20, specifically mentioning the actions/cache@v2 action. Additionally, it warns that actions currently using Node.js 12 will be forced to run on Node.js 16, with a link provided for further information.

Setting Ready for Stage - as above are not breaking any functionality.