Extract js_id to generate valid component names.

[arvind]

#60 only partially fixed the issue of auto generated names. This PR catches the other instance of invalid component names due to dash-separated uuids.

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[coveralls]

Pull Request Test Coverage Report for Build 160

• 0 of 6 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.09%) to 64.05%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lucid/scratch/web/svelte.py	0	6	0.0%

Totals
Change from base Build 154:	-0.09%
Covered Lines:	930
Relevant Lines:	1452

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💛 - Coveralls

[googlebot]

CLAs look good, thanks!

[arvind]

Once we merge, this should probably warrant a version bump @ludwigschubert.

[ludwigschubert]

How did we never merge this? Thanks, @arvind!