ci: add slither static analysis checks

[varunsrin]

Motivation

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Change Summary

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Merge Checklist

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• The PR title adheres to the conventional commits standard
• The PR has been tagged with change type label(s) (i.e. documentation, feature, bugfix, or chore)
• The PR's changes adhere to all the requirements in the contribution guidelines
• This PR does not require changes to the Farcaster protocol

Additional Context

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.78%. Comparing base (8ae8be1) to head (507fd39).
⚠️ Report is 170 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #197   +/-   ##
=======================================
  Coverage   84.78%   84.78%           
=======================================
  Files           8        8           
  Lines         309      309           
  Branches       81       81           
=======================================
  Hits          262      262           
  Misses         45       45           
  Partials        2        2           

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[github-actions]

Coverage after merging varunsrin/add-slither-part-2 into main will be

94.23%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
BundleRegistry.sol	94.29%	83.33%	100%	100%	87, 90
IdRegistry.sol	98.15%	100%	93.75%	98.28%	480
NameRegistry.sol	94.56%	100%	87.10%	92.39%	1072, 1081, 337, 339, 341, 343, 346, 348–349, 351–352, 354–355, 357

[varunsrin]

closing for now, don't think we want slither in ci just yet