Re-add fetch polyfill (#727)

Removed in #367, but core-js does not include fetch, and eslint-plugin-compat just doesn't seem to complain when inside an if block.

.eslintrc.json

@@ -5,6 +5,15 @@
         "es2021": true
     },
     "settings": {
-        "polyfills": ["URL", "Promise", "navigator", "Uint8Array", "performance", "location.hostname", "document.body"]
+        "polyfills": [
+            "URL",
+            "Promise",
+            "navigator",
+            "Uint8Array",
+            "performance",
+            "location.hostname",
+            "document.body",
+            "fetch"
+        ]
     }
 }

README.md

@@ -142,3 +142,5 @@ Copyright (c) 2018 Norbert Renner and [contributors](https://github.com/nrenner/
     [CC0-1.0 License](https://github.com/ideditor/temaki/blob/main/LICENSE.md)
 -   [leaflet-osm-notes](https://github.com/osmlab/leaflet-osm-notes)
     [The Unlicense](https://github.com/osmlab/leaflet-osm-notes/blob/gh-pages/LICENSE)
+-   [Fetch polyfill](https://github.com/Github/fetch)  
+    Copyright (c) 2014-2016 GitHub, Inc.; [MIT License](https://github.com/github/fetch/blob/master/LICENSE)

package.json

@@ -84,7 +84,8 @@
         "regenerator-runtime": "0.13.11",
         "togpx": "nrenner/togpx#722d291",
         "tokml": "0.4.0",
-        "url-search-params": "1.1.0"
+        "url-search-params": "1.1.0",
+        "whatwg-fetch": "^3.6.2"
     },
     "devDependencies": {
         "@babel/cli": "7.19.3",

yarn.lock

@@ -12602,6 +12602,11 @@ whatwg-encoding@^2.0.0:
   dependencies:
     iconv-lite "0.6.3"
 
+whatwg-fetch@^3.6.2:
+  version "3.6.2"
+  resolved "https://registry.yarnpkg.com/whatwg-fetch/-/whatwg-fetch-3.6.2.tgz#dced24f37f2624ed0281725d51d0e2e3fe677f8c"
+  integrity sha512-bJlen0FcuU/0EMLrdbJ7zOnW6ITZLrZMIarMUVmdKtsGvZna8vxKYaexICWPfZ8qwf9fzNq+UEIZrnSaApt6RA==
+
 whatwg-mimetype@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/whatwg-mimetype/-/whatwg-mimetype-3.0.0.tgz#5fa1a7623867ff1af6ca3dc72ad6b8a4208beba7"