feat: add weather map and wind tools

Add get_weather_map, which returns the latest NOAA radar, satellite or
lightning map over an area as an image, choosing a window the image
route accepts and reporting areas outside the product's coverage, and
get_wind, which samples GFS or IFS wind at a location with the wind
layer's own grid sampling.

src/tools/results.js

@@ -41,3 +41,11 @@ export function thinEvenly(items, max) {
     (_, index) => items[Math.round(index * step)],
   );
 }
+
+/** Base64-encode bytes with the platform's btoa, in chunks. */
+export function toBase64(bytes) {
+  let binary = '';
+  for (let offset = 0; offset < bytes.length; offset += 0x8000)
+    binary += String.fromCharCode(...bytes.subarray(offset, offset + 0x8000));
+  return btoa(binary);
+}