Add --hide-unchanged option to hide unchanged SVGs

[viralcodex]

FIXES: #2050
Introduces the --hide-unchanged CLI option to suppress output for SVG files that remain unchanged after optimization. Includes tests to verify that only optimized files are shown when the option is enabled.

Console Outputs:

coa % npx svgo --folder testFolderUnchangedSvg -h --output temp/
Processing directory 'testFolderUnchangedSvg':


optimizable.svg:
Done in 5 ms!
0.268 KiB - 61.3% = 0.104 KiB

----------------------------------------

coa % npx svgo --folder testFolderUnchangedSvg --output temp/ 
Processing directory 'testFolderUnchangedSvg':


optimizable.svg:
Done in 4 ms!
0.268 KiB - 61.3% = 0.104 KiB

unchanged.svg:
Done in 0 ms!
0.104 KiB - 0% = 0.104 KiB

[viralcodex]

Hi @SethFalco,
I have implemented the requested enhancement in the PR, please have a look and let me know at your convenience.

Thanks.