feat: Quickstart and client for Plain JS Script Tags

[clockwork-tien]

Description of Changes

The PR implements the following updates:

• Create a quickstart guide and client support for using SpacetimeDB directly in browser with script tags
• A template to easily work with/test the implementation and get started with script tags

The bundle is served via https://unpkg.com/spacetimedb@latest/dist/browser.bundle.js, which only works after the package is published to npm, therefore to test locally we can use the browser-ts template and local bundle:

1. Build local bundle

cd crates/bindings-typescript
pnpm install
pnpm build

2. Use local bundle built in templateindex.html (swap the URL from unpkg)

- <script src="https://unpkg.com/spacetimedb@latest/dist/browser.bundle.js"></script>
+ <script src="../../crates/bindings-typescript/dist/browser.bundle.js"></script>

3. Open browser-ts/index.html directly in browser along with spacetime start + publish the module spacetime publish --project-path spacetimedb browser-ts

Screenshots

API and ABI breaking changes

Expected complexity level and risk

Testing

[clockwork-tien]

@cloutiertyler Thank you, I have applied the changes from #4167, merged/resolved conflicts and did a minor template description update. The PR is ready for review.