Mercurial gets a new website!

[Raphaël Gomès]

Hello all,

The https://mercurial-scm.org website had been in a state of abandon for 
many years now, and much of the information it contained was either 
out-of-date or plain wrong. This gave the wrong impression of the 
current (active) state of the project, and wasn't that helpful altogether.

To that end, we have finally just released a new version of the website! 
Thanks a ton to Pierre Augier who was behind most of the work and pushed 
us to actually do this before hell freezes over.

A few notes:
     - It's still a work-in-progress, many small(er) things have been 
copy-pasted and need revising
     - If anything critical is missing, please reach out here or via our 
Matrix channel over at #mercurial:matrix.org
     - Contributions welcome over at 
https://foss.heptapod.net/mercurial/hg-website
     - Bug tracking is done at 
https://foss.heptapod.net/mercurial/hg-website/-/issues

Raphaël