Bump Periplum engine to v0.3.2 (fix marker scatter) + Built-with-Periplum badge

[cmehat]

Follow-up to #7 (which is already merged). Two commits didn't make it in because they were pushed after #7 merged:

• Bump engine v0.3.0 → v0.3.2 — picks up the opt-in longitude-unwrap fix (v0.3.1) so the protocol-city markers stay at their true positions instead of scattering across world-copies, plus other engine fixes.
• Built-with-Periplum badge in the README.

No behavioural change beyond the engine bump.

[Copilot]

Pull request overview

Bumps the Periplum engine version used by the GitHub Pages map to pick up upstream fixes (notably the marker scatter fix), and adds a “Built with Periplum” badge to the repository README.

Changes:

• Update Periplum engine CDN reference from v0.3.0 to v0.3.2 in the published site.
• Add a “Built with Periplum” badge under the main README heading.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
README.md	Adds a Periplum badge to highlight the engine used by the project.
docs/index.html	Updates the Periplum CDN URL to v0.3.2 for the map runtime.

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[cmehat]

Good catch — valid and consistent with the SRI-pinned Leaflet assets, and especially relevant since the engine is pinned by a (mutable) tag.

Fixed: added integrity="sha384-…" + crossorigin="anonymous" to the Periplum engine <script> here, and applied the same across all Periplum consumers and the template. To keep this from going stale under the auto-upgrade model, the template's "Upgrade Periplum" workflow now recomputes the SRI hash whenever it bumps the engine version, so the pinned hash and the pinned tag always match.