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Resolves #14438
Resolves #10826

This PR makes it possible to use Svelte on pages which require TrustedTypes support via their CSP by wrapping assignments to innerHTML in a TrustedTypePolicy called svelte-trusted-html if the TrustedTypes API exists.

Servers can allowlist the policy by setting require-trusted-types-for 'script'; trusted-types svelte-trusted-html in their Content-Security-Policy header.

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Tests and linting

Note: I haven't run the tests since I don't have pnpm setup properly.

I have tested that:

1. A project with a CSP fails with Tip of Tree Svelte
2. That project works when installing this revision of Svelte
3. The project (with this revision) works in Browsers with no TrustedTypes support (i.e. Firefox, Safari)

• Run the tests with pnpm test and lint the project with pnpm lint

My test project is here: https://github.com/fallaciousreasoning/svelte-tt-test/blob/master/src/routes/%2Bpage.server.js

The only changes to the default project is adding the CSP in src/routes/page.server.js