Added filemtime to merged JS/CSS hash calculation algorithm

[boesbo]

Description (*)

Add the timestamp of the files in the MD5 HASH generation criteria of the files.

Fixed Issues (if relevant)

1. Fixes OpenMage/magento-lts#4003

Questions or comments

Contribution checklist (*)

• [X] Pull request has a meaningful description of its purpose
• [X] All commits are accompanied by meaningful commit messages
• [X] All automated tests passed successfully (all builds are green)
• [X] Add yourself to contributors list

[boesbo]

If you can I ask you for a review @fballiano

[boesbo]

@fballiano I improved the PR. There was some confusion with the variable name, so your question was legitimate. I have made the code clearer and accepted your suggestion not to run filemtime() several times;

[fballiano]

@boesbo great, I'll test it out a bit

[boesbo]

Non mi piace il modo in cui funziona l'unione per impostazione predefinita in OM, ma questo è un altro argomento, ho testato questo PR e fa quello che afferma e penso che sia ok unire

It is only an improvement of the current functionality in view of a modern (now current) management of these assets in the browser cache. Thx!

[boesbo]

If you can I ask you for a review @kasper-agg

[fballiano]

I'll merge this in a couple of days if there's none against

[kasper-agg]

If you can I ask you for a review @kasper-agg

What @fballiano already mentioned, the whole merging thing is another topic, your PR fixes the current issue at hand :+1: