Move content to documentation sites

[umarcor]

~Blocked by chipsalliance/f4pga#531 and SymbiFlow/f4pga-arch-defs#2497.~

The main documentation and the documentation of arch-defs were updated:

• https://f4pga.readthedocs.io/en/latest/community.html
• https://f4pga.readthedocs.io/en/latest/how.html
• https://f4pga.readthedocs.io/en/latest/status.html
• https://f4pga.readthedocs.io/en/latest/getting-started.html
• https://f4pga.readthedocs.io/projects/arch-defs/en/latest/bitdoc/index.html

Therefore, we can now proceed with removing the content duplicated in the website, and replace it with direct links to the sections above.

See https://umarcor.github.io/f4pga-website/. Note the links in the navigation bar.