Distribute data with layers instead of data/ dir

This was originally done to make the gitignoring easier, but ended up
being somewhat more complex when trying to include files, so they're
moving out closer to the point of use.

layers/nhl-arenas/get_data.py

@@ -93,5 +93,5 @@ geojson = {
     "features": arenas,
 }
 
-with open("nhl-arenas-data.geojson", "w") as f:
+with open("data.geojson", "w") as f:
     f.write(json.dumps(geojson))

layers/nhl-arenas/layer.js

@@ -4,13 +4,13 @@ import GeoJSON from 'ol/format/GeoJSON.js';
 
 import {Style, Stroke, Circle, Fill} from 'ol/style.js';
 
-import arenaURL from '/data/nhl-arenas-data.geojson?url'; // TODO: remove `?url`?
+import url from './data.geojson?url'; // TODO: remove `?url`?
 
 import visitedArenas from './visited.js'
 
 const vectorLayer = new VectorLayer({
     source: new VectorSource({
-        url: arenaURL,
+        url: url,
         format: new GeoJSON,
     }),
     // TODO: use '✓' and '✗' (or maybe '✔' and '✘') (from https://en.wikipedia.org/wiki/List_of_Unicode_characters#Dingbats)