docs: link hugr-py docs from root README, update copyright

[CalMacCQ]

Adding a link to the HUGR py docs from the README of this repo.

Driveby: fix the out of date copyright. I've used datetime to fix the year rather than hardcoding the value.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.80%. Comparing base (82c25ef) to head (4a24198).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2881   +/-   ##
=======================================
  Coverage   83.80%   83.80%           
=======================================
  Files         267      267           
  Lines       53605    53606    +1     
  Branches    47731    47731           
=======================================
+ Hits        44926    44927    +1     
  Misses       6272     6272           
  Partials     2407     2407           

Flag	Coverage Δ
python	88.47% <100.00%> (+<0.01%)	⬆️
rust	83.23% <ø> (ø)

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[aborgna-q]

This is the README that appears in the crates.io page for the rust library.

The root README is currently symlinked to this, but I think we should make a copy instead, and add the python docs link there (as well as update it to talk about the different libraries, but that can be done later).