Selenium integration tests for CI

[popensesame]

• [x] Write Selenium test for file browser

• [x] Write Selenium test for model editor

• [ ] Refactor ID-based locators to class/name or class/value locators

• [ ] Ensure compatibility with headless browsers to file browser context menu items

• [ ] Integrate Selenium tests into GitHub CI

• [ ] Expand Selenium tests into Opera, Edge, Chrome browsers

• [ ] Expand Selenium tests into MacOS, Windows OS

• [ ] Write Selenium tests for workflow editor

[jdreeve]

• [x] Add IDs to WebElements in /client/templates/pages

• [x] Add IDs to WebElements in /client/templates/includes

• [ ] Add validation test to ensure unique IDs

• [ ] Write Selenium tests

• [ ] Add GitHub action to run Selenium tests