Added keyboard shortcuts for Chrome DevTools CheatSheet (Mac & Windows/Linux)

[abuna1985]

What does this PR do?

Add content to the Chrome Devtool Cheatsheet

Description

I used the [Chrome Developers Docs on keyboard shortcuts] (https://developer.chrome.com/docs/devtools/shortcuts/) as a reference and added more keyboard shortcuts. I also separated Mac and Windows/Linux shortcuts.

Screenshots or Links

Additional context

Fixes #40

Checklist:

• [x] Read our contributing guidelines.
• [x] Search for duplicates.
• [x] Used an informative name for this pull request.

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