Add testing bots

[bilelmoussaoui]

I think we should have two bots:

• One to validate that the urls are returning a valid response and that the pages exists
• One to check and validate the contrast between fg/bg colors used in each application to avoid unreadable texts.

[bilelmoussaoui]

Done, see for an example of the two tests running https://github.com/bilelmoussaoui/revoke.app/runs/723997184