Create GitHub Actions workflow to build and test all the apps

When we update applications like automated package updates, we want to run tests and check if they are passing before merging PRs.

Tests could be as minimal as checking the health status endpoints created in #484 to more expanded versions where we run some unit or browser-based testing.

This issue may be split into multiple PRs, with one PR for every project.

```[tasklist]
### Tasks
- [ ] 25--5-clock
- [ ] american-british-translator
- [ ] anonymous-message-board
- [ ] bar-chart
- [ ] build-a-pinterest-clone
- [ ] cash-register
- [ ] chart-the-stock-market
- [ ] choropleth-map
- [ ] drum-machine
- [ ] exercise-tracker
- [ ] file-metadata-microservice
- [ ] forum-proxy
- [ ] heat-map
- [ ] image-search-abstraction-layer
- [ ] issue-tracker
- [ ] javascript-calculator
- [ ] manage-a-book-trading-club
- [ ] markdown-previewer
- [ ] metric-imperial-converter
- [ ] nightlife-coordination-app
- [ ] p2p-video-chat-application
- [ ] palindrome-checker
- [ ] personal-library
- [ ] personal-portfolio
- [ ] pokeapi-proxy
- [ ] pokemon-search-app
- [ ] product-landing-page
- [ ] random-quote-machine
- [ ] request-header-parser-microservice
- [ ] roman-numeral-converter
- [ ] scatterplot-graph
- [ ] secure-real-time-multiplayer-game
- [ ] stock-price-checker-proxy
- [ ] stock-price-checker
- [ ] sudoku-solver
- [ ] survey-form
- [ ] technical-documentation-page
- [ ] telephone-number-validator
- [ ] timestamp-microservice
- [ ] treemap-diagram
- [ ] tribute-page
- [x] twitch-proxy
- [ ] url-shortener-microservice
- [ ] voting-app
- [ ] weather-proxy
```