Homepage upgrade

**Short description**:
Spice up the most prominent page with the following elements
- [ ] #104 Integrate more screenshots in landing page
- [ ] #101 Code contributions graph
- [ ] #100 'Latest forum posts' list
- [ ] #97 Display list of features on homepage

**Location**:
Homepage

**Why have this**:
See respective issues

**More info**:
[Mock-up on Penpot](https://design.penpot.app/#/view/d1c45d80-3b12-11ec-a516-23056af0be2f?page-id=d1c45d81-3b12-11ec-a516-23056af0be2f&index=0&share-id=84111db0-3b41-11ec-a516-23056af0be2f)

I didn't implement it in the mock-up, but I think we should only display two rows of features by default, and have a 'Show all' button to unhide the other rows.

@ByteHamster What do you think? I indeed opted not to include some of the elements on the homepage I was thinking of first (contributors list, latest version).