Add mamoto tracking to frontend

[spwoodcock]

Fixes #942

For website analytics.

This only activates on the prod setup (fmtm.hotosm.org).
The approach I settled on:

const MatomoTrackingInit = () => {
  useEffect(() => {
    if (import.meta.env.MODE !== 'development' && import.meta.env.BASE_URL === 'fmtm.hotosm.org') {
      return;
    }
    // Set matomo tracking id
    window.site_id = environment.mamotoTrackingId;
​
    // Create optout-form div for banner
    const optoutDiv = document.createElement('div');
    optoutDiv.id = 'optout-form'; // Set an ID if needed
    document.body.appendChild(optoutDiv);
​
    // Load CDN script after
    const script = document.createElement('script');
    script.src = 'https://cdn.hotosm.org/tracking-v3.js';
    document.body.appendChild(script);
    // Manually trigger DOMContentLoaded, that script hooks
    // https://github.com/hotosm/matomo-tracking/blob/9b95230cb5f0bf2a902f00379152f3af9204c641/tracking-v3.js#L125
    script.onload = () => {
      optoutDiv.dispatchEvent(
        new Event('DOMContentLoaded', {
          bubbles: true,
          cancelable: true,
        }),
      );
    };
​
    // Cleanup on unmount
    return () => {
      document.body.removeChild(optoutDiv);
      document.body.removeChild(script);
    };
  }, []);
​
  return null; // Renders nothing
};
​
// The main App render
ReactDOM.render(
  <Provider store={store}>
    <PersistGate loading={null} persistor={persistor}>
      <RouterProvider router={routes} />
      <MatomoTrackingInit />
      <SentryInit />
    </PersistGate>
  </Provider>,
  document.getElementById('app'),
);