feat: extra maplibre layers

[gadomski]

To configure:

 <StacMap
      defaultHref={defaultHref}
      auth={auth}
      stacBrowserUrl={stacBrowserUrl}
      extraLayers={[
        {
          layer: {
            id: "oam-global-coverage",
            type: "fill",
            "source-layer": "globalcoverage",
            minzoom: 0,
            maxzoom: 15,
            filter: ["==", ["geometry-type"], "Polygon"],
            paint: {
              "fill-color": "#d43f3f",
              "fill-opacity": 0.2,
              "fill-outline-color": "#d43f3f",
            },
          },
          source: {
            type: "vector",
            url: "pmtiles://https://s3.amazonaws.com/oin-hotosm-temp/global-coverage.pmtiles",
          },
        },
      ]}
      footer={<Footer version={version} changelog={changelog} />}
    />

Got: