Add a single page router that will redirect all missing requests to index.html

[halkeye]

Tested a bit locally. Seems to work

Created a test to confirm the redirect happens

[halkeye]

Demo: https://customize.jenkins-infra.g4v.dev/
/ doesn't do anything really, but all the other urls work it seems even after a refresh

Problem #1) API_URL was causing //api which isn't a valid api call
Problem #2) On refresh springboot would return 404 for the urls, adding the new wildcard match brings it back to index.html

[martinda]

Thank you very much @halkeye