Fix the resize corner handles in the dark theme.

[seanparsons]

Problem:
The resize corner handles look like empty white boxes in the dark theme.

Fix:
Took the colours from the light theme and copied them into the dark theme.

Commit Details:

• Changed the canvasControlsSizeBoxShadowColor20 and canvasControlsSizeBoxShadowColor50 theme properties.

Manual Tests:
I hereby swear that:

• I opened a hydrogen project and it loaded
• I could navigate to various routes in Play mode

Fixes #6658

[liady]

👏

[github-actions]

Try me

[relativeci]

#15254 Bundle Size — 58.11MiB (~-0.01%).

e716893(current) vs d1d46c1 master#15252(baseline)

Warning

Bundle contains 70 duplicate packages – View duplicate packages

Bundle metrics   2 changes 1 improvement

	Current #15254	Baseline #15252
Initial JS	41.08MiB(~-0.01%)	41.08MiB
Initial CSS	0B	0B
Cache Invalidation	18.17%	18.05%
Chunks	20	20
Assets	22	22
Modules	4172	4172
Duplicate Modules	213	213
Duplicate Code	27.28%	27.28%
Packages	477	477
Duplicate Packages	70	70

Bundle size by type   2 changes 2 improvements

	Current #15254	Baseline #15252
JS	58.1MiB (~-0.01%)	58.1MiB
HTML	7.37KiB (-0.25%)	7.39KiB

Bundle analysis report Branch fix/resize-handles-dark-theme Project dashboard

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[bkrmendy]

Looks great!