Setup for mas build

// FREEBIE

.gitignore

@@ -8,3 +8,4 @@ dist
 config/local.json
 config/local-*.json
 .DS_Store
+*.provisionprofile

build/entitlements.mas.plist

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>com.apple.security.app-sandbox</key>
+    <true/>
+    <key>com.apple.security.network.client</key>
+    <true/>
+    <key>com.apple.security.files.user-selected.read-only</key>
+    <true/>
+    <key>com.apple.security.files.user-selected.read-write</key>
+    <true/>
+  </dict>
+</plist>

package.json

@@ -56,7 +56,8 @@
         "bucket": "updates.signal.org",
         "path": "desktop",
         "acl": "public-read"
-      }
+      },
+      "target": "mas"
     },
     "win": {
       "artifactName": "${productName}-Setup_${version}.${ext}",