Enable app sandbox entitlement

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

build/entitlements.mac.plist

@@ -2,13 +2,6 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-    <!-- Entitlements from electron-builder's defaults
-         (https://github.com/electron-userland/electron-builder/blob/master/packages/app-builder-lib/templates/entitlements.mac.plist)
-         nb. This does *not* include the app sandbox: at the time of adding this file,
-         we were using electron-builder 21.2.0 which does not have the sandbox entitlement.
-         Latest electron-builder does, but it appears to be causing issues:
-         (https://github.com/electron-userland/electron-builder/issues/4390)
-    -->
     <!-- https://github.com/electron/electron-notarize#prerequisites -->
     <key>com.apple.security.cs.allow-jit</key>
     <true/>
@@ -17,8 +10,19 @@
     <key>com.apple.security.cs.disable-library-validation</key>
     <true/>
 
-    <!-- Our own additional entitlements (we need to access the camera and
-        mic for VoIP calls -->
+    <!-- Enable the app sandbox -->
+    <key>com.apple.security.app-sandbox</key>
+    <true/>
+
+    <!-- Allow opening outgoing network connections -->
+    <key>com.apple.security.network.client</key>
+    <true/>
+
+    <!-- Allow opening & saving files for upload & download -->
+    <key>com.apple.security.files.user-selected.read-write</key>
+    <true/>
+
+    <!-- Access to camera & microphone for calls ->
     <key>com.apple.security.device.camera</key>
     <true/>
     <key>com.apple.security.device.audio-input</key>