Add Features: Refactoring and Variable Highlighting

[Caephler]

• Cmd+M / Ctrl+M will highlight all instances of the identifier that the cursor is currently at, after which typing a new name should simultaneously change all instances of that identifier. Pressing the Esc key will bring the editor back to having only one cursor. Alternatively, clicking anywhere on the editor will make the additional cursors disappear.

• Whenever the cursor moves or the code changes, a faint dashed box will surround all instances of it for easier identifying of which variable you are looking at.

[coveralls]

Pull Request Test Coverage Report for Build 4122

• 9 of 38 (23.68%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.08%) to 36.951%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/components/workspace/Editor.tsx	5	34	14.71%

Totals
Change from base Build 4107:	-0.08%
Covered Lines:	2745
Relevant Lines:	6643

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💛 - Coveralls

[martin-henz]

Nice job. good to see the comments and the link to the Ace editor sources.