chore: add Prettier and Spotless checks, format files

[ThirdEyeSqueegee]

Issue #, if available:
N/A

Description of changes:

• Add Prettier action for .md and .yml files
• Add Spotless action for .java files (palantir-java-format)
• Add formatting instructions to CONTRIBUTING.md
• Remove push triggers from workflows
• Format files
• Add rutajdash/prettier-cli-action to actions allowlist

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 61.11111% with 7 lines in your changes missing coverage. Please review.

Project coverage is 25.40%. Comparing base (0d48fb8) to head (c683a70).
Report is 2 commits behind head on v2.

Files with missing lines	Patch %	Lines
...ws/secretsmanager/sql/AWSSecretsManagerDriver.java	0.00%	5 Missing ⚠️
...manager/sql/AWSSecretsManagerPostgreSQLDriver.java	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                 v2     #274      +/-   ##
============================================
+ Coverage     24.86%   25.40%   +0.54%     
  Complexity       41       41              
============================================
  Files            12       12              
  Lines           366      370       +4     
  Branches         45       46       +1     
============================================
+ Hits             91       94       +3     
- Misses          273      274       +1     
  Partials          2        2              

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