Support `webp` images

Problem to solve

White working on a project, I've discovered that as of right now, .webp images are not yet rendering in READMEs etc, but rather a download option is being shown. It would be awesome to be able to use this new format for everything now that both Firefox and Chromium support it.

Target audience

• Sasha, Software Developer, https://design.gitlab.com/research/personas#persona-sasha

Further details

(see above)

Proposal

Probably, WebP images should be rendered by default, and a fallback such as modernizr could be used if the browser does not support it.

What does success look like, and how can we measure that?

If the images would render on both Firefox and Chrome, that would count as success, I guess.

Links / references

• A test repo

Test System

[pojntfx@pojntfx-x230-fedora ~]$ firefox --version
Mozilla Firefox 65.0

[pojntfx@pojntfx-x230-fedora ~]$ google-chrome --version
Google Chrome 72.0.3626.81

[pojntfx@pojntfx-x230-fedora ~]$ screenfetch
           /:-------------:\          pojntfx@pojntfx-x230-fedora
        :-------------------::        OS: Fedora 29 TwentyNine
      :-----------/shhOHbmp---:\      Kernel: x86_64 Linux 4.19.15-300.fc29.x86_64
    /-----------omMMMNNNMMD  ---:     Uptime: 2d 9h 34m
   :-----------sMMMMNMNMP.    ---:    Packages: 2118
  :-----------:MMMdP-------    ---\   Shell: bash 4.4.23
 ,------------:MMMd--------    ---:   Resolution: 1366x768
 :------------:MMMd-------    .---:   DE: GNOME
 :----    oNMMMMMMMMMNho     .----:   WM: GNOME Shell
 :--     .+shhhMMMmhhy++   .------/   WM Theme:
 :-    -------:MMMd--------------:    GTK Theme: Adwaita-dark [GTK2/3]
 :-   --------/MMMd-------------;     Icon Theme: Adwaita
 :-    ------/hMMMy------------:      Font: Cantarell 11
 :-- :dMNdhhdNMMNo------------;       CPU: Intel Core i5-3320M @ 4x 3.3GHz [61.0°C]
 :---:sdNMMMMNds:------------:        GPU: Mesa DRI Intel(R) Ivybridge Mobile
 :------:://:-------------::          RAM: 3040MiB / 7791MiB
 :---------------------://