Add web support to place_tracker (#550)

* enable web for place_tracker

* add place_tracker symlink

* add generated_plugin_registrant.dart

* update google_maps_flutter_web to fix pins not showing

* add place_tracker to peanut.yaml

* upgrade place_tracker dep

* use a 32 pixel square

* Apply zoom to selected category when the PlaceMapState updates. This fixes a grey screen issue in web, after saving a place.

* pub upgrade

* run pub upgrade

* use published versions of packages

* remove lib/generated_plugin_registrant.dart

* add newline

* add web API key to README

Co-authored-by: David Iglesias Teixeira <ditman@gmail.com>

place_tracker/web/manifest.json

@@ -0,0 +1,23 @@
+{
+    "name": "place_tracker",
+    "short_name": "place_tracker",
+    "start_url": ".",
+    "display": "standalone",
+    "background_color": "#0175C2",
+    "theme_color": "#0175C2",
+    "description": "A new Flutter project.",
+    "orientation": "portrait-primary",
+    "prefer_related_applications": false,
+    "icons": [
+        {
+            "src": "icons/Icon-192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "icons/Icon-512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ]
+}