Update README to include extension packages

[kishannsangani]

Added extension packages search link on packagist.

[codecov]

Codecov Report

Merging #812 (f523ed3) into main (77838b3) will not change coverage.
The diff coverage is n/a.

❗ Current head f523ed3 differs from pull request most recent head 1b1c2a5. Consider uploading reports for the commit 1b1c2a5 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #812   +/-   ##
=========================================
  Coverage     81.03%   81.03%           
  Complexity     1825     1825           
=========================================
  Files           225      225           
  Lines          4687     4687           
=========================================
  Hits           3798     3798           
  Misses          889      889           

Flag	Coverage Δ
7.4	81.03% <ø> (ø)
8.0	81.06% <ø> (ø)
8.1	81.06% <ø> (ø)

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