Add composer-require-checker CI + Fix BC checker

[xepozz]

Added composer-require-checker according to yiisoft/actions#9

[codecov]

Codecov Report

Base: 93.19% // Head: 90.96% // Decreases project coverage by -2.23%⚠️

Coverage data is based on head (e637aed) compared to base (a62ae3d).
Patch coverage: 50.00% of modified lines in pull request are covered.

❗ Current head e637aed differs from pull request most recent head 1c5aaac. Consider uploading reports for the commit 1c5aaac to get more accurate results

Additional details and impacted files

@@ Coverage Diff @@## master #49 +/- ##
============================================
- Coverage 93.19% 90.96% -2.23% - Complexity 68 71 +3 
============================================
Files 1 1 Lines 147 155 +8 ============================================
+ Hits 137 141 +4 - Misses 10 14 +4 

Impacted Files	Coverage Δ
src/FileCache.php	90.96% <50.00%> (-2.23%)	⬇️

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