docs: improve warning on short auto sizing #50

Job	Run time
Input 'slug-maxlength' (macos-latest)	7s
Check v4 compatibility (macos-latest)	9s
Input 'slug-maxlength' (ubuntu-latest)	5s
Display produced variables (macos-latest)	12s
Check v4 compatibility (ubuntu-latest)	5s
Input 'slug-maxlength' (windows-latest)	18s
Input 'short-length' (macos-latest)	12s
Display produced variables (ubuntu-latest)	8s
Check v4 compatibility (windows-latest)	21s
Input 'short-length' (ubuntu-latest)	6s
Display produced variables (windows-latest)	13s
Input 'short-length' (windows-latest)	21s
Display produced variables (without checkout) (macos-latest)	8s
Display produced variables (without checkout) (ubuntu-latest)	5s
Display produced variables (without checkout) (windows-latest)	14s
Check v4 compatibility (without checkout) (macos-latest)	9s
Check v4 compatibility (without checkout) (ubuntu-latest)	5s
Check v4 compatibility (without checkout) (windows-latest)	17s
Input 'short-length' (without checkout) (macos-latest)	9s
Input 'short-length' (without checkout) (ubuntu-latest)	6s
Input 'short-length' (without checkout) (windows-latest)	23s
release	18s
	4m 11s

Provide feedback