fix #2282: Add Check for Proxy support

[chiefcll]

Summary

On older browsers (Chrome < 49) Proxy is not supported. When using core-js to polyfill features - $PROXY in s always returns true, leading to proxy being true and Solid trying to use Proxy even though the browser doesn't support it.

How did you test this change?

I've tested these changes using lambdatest.com.

https://github.com/lightning-tv/solid-demo-app

[changeset-bot]

🦋 Changeset detected

Latest commit: c5b6ce2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
solid-js	Patch
test-integration	Patch

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[coveralls]

Pull Request Test Coverage Report for Build 10999900293

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• 16 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.009%) to 93.351%

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Files with Coverage Reduction	New Missed Lines	%
packages/solid/store/src/mutable.ts	1	93.87%
packages/solid/src/reactive/signal.ts	15	93.14%

Totals
Change from base Build 10692001464:	0.009%
Covered Lines:	4200
Relevant Lines:	4433

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💛 - Coveralls