[DOC] updating the README for the 2.0 release

[fkiraly]

This PR updates the README for the 2.0 release:

• 2.0 code snippets
• updated community and contribution links
• updated documentation references

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -1.96% ⚠️

Comparison is base (0a67ed7) 71.31% compared to head (9d71a5b) 69.36%.
Report is 1 commits behind head on main.

❗ Current head 9d71a5b differs from pull request most recent head 2e88d0f. Consider uploading reports for the commit 2e88d0f to get more accurate results

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
- Coverage   71.31%   69.36%   -1.96%     
==========================================
  Files          92       92              
  Lines        4863     4863              
  Branches      893      893              
==========================================
- Hits         3468     3373      -95     
- Misses       1172     1272     +100     
+ Partials      223      218       -5     

see 3 files with indirect coverage changes

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