Support templates hosted on SourceHut and GitLab (e.g. wofi)

[paul-ri]

As described in the commit:

The template source from base16-templates-source contains a link to a SourceHut repository (e.g. wofi) that doesn't exist on GitHub. Only GitHub is supported at the moment by base16-universal-manager.

This is a commit with sane defaults that should work for now. But later we could add support for user settings to set the raw base url as well as the main repository branch (which isn't 'master' by default in most new repos).

Notes

• First time I write some code in Go... Happy to hear any suggestions on doing things differently.
• Can you also update the wiki? I've pushed some changes adding wofi in my fork of your wiki

git clone https://github.com/pinpox/base16-universal-manager.wiki
git pull https://github.com/paul-ri/base16-universal-manager.wiki.git
git push

Testing done

• Ran tests with IDE :heavy_check_mark:
• The following config was failing, but now isn't :heavy_check_mark:

  
  wofi:
  enabled: true
  files:
    default:
      path: ~/.config/wofi/style.css
      mode: rewrite

[codecov[bot]]

Codecov Report

Merging #58 (7ca067c) into master (3d6b1d7) will increase coverage by 2.57%. The diff coverage is 82.35%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
+ Coverage   15.78%   18.36%   +2.57%     
==========================================
  Files           5        5              
  Lines         437      452      +15     
==========================================
+ Hits           69       83      +14     
- Misses        349      350       +1     
  Partials       19       19              

Impacted Files	Coverage Δ
template.go	22.22% <82.35%> (+22.22%)	:arrow_up:

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[paul-ri]

PR will fix #43