Updating to 102 documentation updates

[kewisch]

Hey @jobisoft , @metasansana,

I've done a number of changes to this document, including:

• syntax highlighting for js (not sure if gitbook makes use of this?)
• More examples on the changes. I had to look a few things up when implementing changes which was time consuming.
• Use of Thunderbird vs TB, I think it makes sense to avoid shortcuts here.
• More elaborate docs on what to change as a provider and some re-ordering of sections to accommodate.

I hope it is ok I did not split up the commits on this.

[kewisch]

Apologies also, my github notification emails are a mess. I will likely miss a lot of them. If you'd like me to make changes and I'm not responding I'd appreciate a ping on matrix.

[jobisoft]

Thanks for making the documentation better!