This is very welcoming sort of page. Good job!

Compare this to most open source projects of this scale, where you will have people just tell you "to look it up in the wiki".

This wiki, if you're lucky enough to find it and find the right article, then often only has a 50% chance of being up to date and therefore missing some crucial information, causing you to spend days getting your build-setup still not working.

Before you even get to contributing, you're already meeting roadblocks on roadblocks and a dismissive attitude to your offer for help.

This on the contrary, looks very inviting. Kudos to Mozilla :)