Update and expand information about building Gitea

[zeripath]

The current information on gitea.io for building and hacking on is inadequate. This PR expands on this and provides some more information.

Signed-off-by: Andrew Thornton art27@cantab.net

[codecov-io]

Codecov Report

Merging #6019 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6019      +/-   ##
==========================================
- Coverage   38.87%   38.86%   -0.01%     
==========================================
  Files         345      345              
  Lines       49491    49491              
==========================================
- Hits        19239    19237       -2     
- Misses      27471    27473       +2     
  Partials     2781     2781

Impacted Files	Coverage Δ
models/repo_list.go	63.29% <0%> (-1.27%)	⬇️

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[kolaente]

Looks good so far, some small nits though.

Could you also add a note about adding new config options to the docs? (mainly where to put them)

[zeripath]

I've made some changes to hacking:

I've added information about adding settings. (Albeit perhaps a little cursory as I note that @lunny has a current PR open to refactor modules/setting/setting.go )

I've added a note to say you will need make (I thought I had put that in already. oops)

I've put a bit more detail in about swagger and go-swagger.

[zeripath]

Adjusted the clarifying note about automatic build dependencies.

I have avoided mentioning vendor so far because I expect that could be quite complex. We would likely need to talk about dep ensure, make test-vendor and gopkg.toml.

There is in general a lack of documentation about hacking on the UI too. This could be done as another pr.

[sapk]

Vendoring and GOPATH will also change when we migrate to go mod

[techknowlogick]

Thanks for updating the docs!! 🎊

A few nits, but otherwise looks fantastic!

[zeripath]

I just noticed that we'd added postcss so added a little thing about that. I think it's probably ready to merge now.

[zeripath]

Thanks peeps. Hopefully people will find this helpful. I guess we just need to try to keep it up to date.

I'll pop a comment on @typeless go module pr to suggest that a bit of information to hacking and install is put down.