docs(readme): add security disclaimer

[lirantal]

Description

It may not be clear as to what is the scope of malicious package trust that this security linter helps with.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] Documentation
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Related Issue

Fixes #36

[codecov-io]

Codecov Report

Merging #56 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #56   +/-   ##
=======================================
  Coverage   97.88%   97.88%           
=======================================
  Files          11       11           
  Lines         189      189           
  Branches       29       29           
=======================================
  Hits          185      185           
  Misses          4        4

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