Use ResizeObserver in MonacoEditor component

[meyer]

Problem

MonacoEditor only recalculates its bounds when the browser window is resized. The container div might change size arbitrarily however, so we need to use something that reacts to the container size changes instead.

Solution

Use a ResizeObserver

Result

MonacoEditor resizes correctly when its container is resized.

[coveralls]

Pull Request Test Coverage Report for Build 3700605465

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 61.089%

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Totals
Change from base Build 3698944514:	0.0%
Covered Lines:	15801
Relevant Lines:	24117

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💛 - Coveralls