Add Paul's presentation to Videos

See merge request !97

Update expiry dates of PGP keys, add release signing key

See merge request !96

Add articles to press page

See merge request !95

Bump Briar Desktop version to 0.2.1

Closes #38

See merge request !94

Show date and author for news pages only

See merge request !93

Move myself to the list of Past Contributors

See merge request !92

Regarding the board that's the best way I've come up with to record my
membership there. An alternative would have been to create a list of
past legislative periods, but I can imagine that to become quite large
in time. Still, I'm open to change this according to others' opinions.

Once this is merged, I'll:
* leave all GitLab groups
* leave all Mattermost channels except the Prototype Fund/mentoring related ones
* remove my access to all Briar infrastructure (that's only desktop.briarproject.org)
* remove my access to YouTube and PeerTube
* remove my access to Transifex

Regarding Transifex, some translators might finish their translations
for my talk in the next months and I hope that @akwizgran or @grote (the
only other ones with access to YouTube) will upload the subtitles there.
Thank you!

MR as per
https://chat.briarproject.org/briar/pl/6qa5wndxzpdcxc8rcd568keqwy.

Restyle the news index page and posts

See merge request !91

Compare Desktop's features with Android's one

Closes #36

See merge request !83

Add link to quick start guide from How It Works page

See merge request !89

Update press page

See merge request !88

Update news item, restore Google Play links

See merge request !86

Add status update for Google Play removal

See merge request !85

Update hashsums for 0.2.0 Desktop release

See merge request !84

Add Prototype Fund interview to press page

See merge request !82