[MMU-UI]: resolve build warnings

The Angular build (npm start/npm run build) currently producing many warnings.

1. CSS Autoprefixer warnings
2. Angular NG8107 - unnecessary optional chaining
3. CommonJS dependency warnings (surely impacting the bundle size)

[pragnyanramtha]

worked on this and raised prs at

PSMRI/MMU-UI#335 and PSMRI/MMU-UI#336