Add support for outputting relative paths in patches

[cottsay]

For workspace and configuration relocatability, we may want to get relative paths rather than absolute paths.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 62.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.89%. Comparing base (9c431a3) to head (dece077).

Files with missing lines	Patch %	Lines
pallet_patcher/command.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
==========================================
- Coverage   81.06%   80.89%   -0.17%     
==========================================
  Files           6        6              
  Lines         264      267       +3     
  Branches       68       68              
==========================================
+ Hits          214      216       +2     
- Misses         31       32       +1     
  Partials       19       19              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.