docs: minor documentation changes

[avik-pal]

• Boltz.jl docs removed to avoid a deadlock when releasing Lux 1.0 (see refactor: general cleanup of internals and documentation Boltz.jl#47)
• landing page with more instructions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 33.97%. Comparing base (6fab339) to head (6378552).
Report is 2 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (6fab339) and HEAD (6378552). Click for more details.

HEAD has 41 uploads less than BASE

Flag	BASE (6fab339)	HEAD (6378552)
	49	8

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #855       +/-   ##
===========================================
- Coverage   93.73%   33.97%   -59.77%     
===========================================
  Files          59       59               
  Lines        2954     2914       -40     
===========================================
- Hits         2769      990     -1779     
- Misses        185     1924     +1739     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.