Implement firstindex and lastindex

[blegat]

• Needs tests

This is needed for JuliaAlgebra/MultivariateBases.jl#57

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.96%. Comparing base (dd6c877) to head (b7654e7).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bases_fixed.jl	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   84.15%   83.96%   -0.20%     
==========================================
  Files          15       15              
  Lines         871      873       +2     
==========================================
  Hits          733      733              
- Misses        138      140       +2     

☔ View full report in Codecov by Sentry.
📢 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.

[kalmarek]

waiting for the test ;)