various test_site fixes

[z-andrei-pak]

Here are some changes I had to do in order to run test_site.bash

I'm not sure the solutions are 100% correct. Please, check them and I revert some or all of them in case they are wrong.

.gitignore - one more file appears during script run Dockerfile - apparently some nodejs dependency needs version >=10 (I don't remember which one) main.css - this one is mystery for me, but it gets updated during script run gulpfile.js - this change prevents http server from reloading each few seconds