Fix 66 67

Use site.baseurl instead of site.url to include /fdroid-website if appropriate.

Also set a max-width on all images. Seems silly to have any image going over the edge of its parent unless we explicitly want it to. This prevents the screenshot on the home page being too big on mobile browsers.

• https://pserwylo.gitlab.io/fdroid-website
• https://fix-66-67-fdroid-website-pserwylo.surge.sh/fdroid-website/

Fixes #66 (closed), #67 (closed).