Assorted small doc fixes

[delucchi-cmu]

• add link to contribution guide and CoC in the pull request template
• add link to CoC in contribution guide
• fix import path in catalog import arguments in argument descriptions page
• set contribution guide to use .setup_dev.sh script
• remove mac-specific healpy installation (no longer needed)
• suggest larger threshold for slightly larger leaf parquet files on catalog import
• provider pointers to where input reader kwargs will be passed

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.52%. Comparing base (3f7a423) to head (9639064).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #310 +/- ## ======================================= Coverage 99.52% 99.52% ======================================= Files 25 25 Lines 1274 1274 ======================================= Hits 1268 1268 Misses 6 6 ```

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