feat: add svelte/restrict-mustache-expressions rule

[AlbertMarashi]

Being able to use non-stringifiable objects in string contexts is a major footgun and surface area for bugs. This new rule creates lint errors for situation such as:

<script lang="ts">

let foo = {
  bar: true
}
</script>
<a href="/foo/{foo}">foo</a>

where the href is serialised into "/foo/[object Object]" which is almost never wanted behavior, and these types of bugs can easily be introduced through refactoring

Related: #747

[changeset-bot]

🦋 Changeset detected

Latest commit: e1c168d

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

This PR includes changesets to release 1 package

Name	Type
eslint-plugin-svelte	Minor

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