Add sb3 mime type and file open support

edu.mit.Scratch.desktop

@@ -1,8 +1,10 @@
 [Desktop Entry]
 Name=Scratch
 Comment=Imagine, Program, Share
-Exec=scratch-desktop
+Exec=scratch-desktop %f
 Terminal=false
 Type=Application
 Icon=edu.mit.Scratch
 Categories=Development;
+StartupWMClass=Scratch
+MimeType=application/x.scratch.sb3

edu.mit.Scratch.mime.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
+  <mime-type type="application/x.scratch.sb3">
+    <comment>Scratch 3 Project</comment>
+    <acronym>SB3</acronym>
+    <generic-icon name="edu.mit.Scratch" />
+    <glob pattern="*.sb3" />
+  </mime-type>
+</mime-info>

edu.mit.Scratch.yaml

@@ -95,16 +95,19 @@ modules:
       - type: script
         dest-filename: scratch-desktop.sh
         commands:
-          - 'cd /app/scratch'
-          - 'zypak-wrapper ./scratch-desktop'
+          - cd /app/scratch
+          - zypak-wrapper ./scratch-desktop "$@"
 
   - name: appdata
     buildsystem: simple
     build-commands:
-      - 'install -Dm 644 edu.mit.Scratch.appdata.xml /app/share/metainfo/edu.mit.Scratch.appdata.xml'
-      - 'install -Dm 644 edu.mit.Scratch.desktop /app/share/applications/edu.mit.Scratch.desktop'
+      - install -Dm 644 edu.mit.Scratch.appdata.xml /app/share/metainfo/edu.mit.Scratch.appdata.xml
+      - install -Dm 644 edu.mit.Scratch.desktop /app/share/applications/edu.mit.Scratch.desktop
+      - install -Dm 644 edu.mit.Scratch.mime.xml /app/share/mime/packages/edu.mit.Scratch.mime.xml
     sources:
       - type: file
         path: edu.mit.Scratch.appdata.xml
       - type: file
         path: edu.mit.Scratch.desktop
+      - type: file
+        path: edu.mit.Scratch.mime.xml