microbit: enable sign-in & cloud sync (#4970)

Author: eanders-ms

.gitignore

@@ -19,6 +19,7 @@ electron-out
 hexcache
 build
 crowdinstats.csv
+.pxt/
 
 *.user
 *.sw?

docs/static/providers/github-mark.png

@@ -25,12 +25,35 @@
         "thumbnails": true,
         "publishing": true,
         "importing": true,
+        "showBadges": false,
         "preferredPackages": [
             "Microsoft/pxt-neopixel"
         ],
         "githubPackages": true,
         "cloudProviders": {
-            "github": {}
+            "github": {
+                "id": "github",
+                "name": "GitHub",
+                "icon": "/static/providers/github-mark.png",
+                "identity": false,
+                "order": 3
+            },
+            "microsoft": {
+                "id": "microsoft",
+                "name": "Microsoft",
+                "icon": "/static/providers/microsoft-logo.svg",
+                "identity": true,
+                "redirect": true,
+                "order": 1
+            },
+            "google": {
+                "id": "google",
+                "name": "Google",
+                "icon": "/static/providers/google-logo.svg",
+                "identity": true,
+                "redirect": true,
+                "order": 2
+            }
         }
     },
     "compile": {
@@ -396,6 +419,7 @@
             "bluetoothPartialFlashing",
             "simScreenshot",
             "simGif",
+            "identity",
             "blocksErrorList"
         ],
         "bluetoothUartFilters": [