add multi-links support and logos for bitbucket, git, scm and sourcef…

[rodrigomelo9]

This PR adds support for multiple links per group (gh, gl, docs, web). It also adds support for bb, sf, git and scm (with special icons for them).

Something like that:

links:
  gh:
  - aaa/bbb
  - ccc/ddd
  gl: eee/fff
  docs: https://www.ggg.com
  web:
  - https://www.hhh.com
  - https://www.iii.com
  scm: https://www.jjj.com
  bb: kkk/lll
  sf: gtkwave
  git:
  - https://git-repo1.com
  - https://git_repo2.com

Produces:

Closes #172

[umarcor]

Thanks!