Populate content_rating tag

Author: thebaer

data/com.github.writeas.writeas-gtk.appdata.xml

@@ -47,7 +47,35 @@
       <image type="source">https://write.as/img/screens/gtk/monospace.png</image>
     </screenshot>
   </screenshots>
-  <content_rating type="oars-1.1" />
+  <content_rating type="oars-1.1">
+    <content_attribute id="violence-cartoon">none</content_attribute>
+    <content_attribute id="violence-fantasy">none</content_attribute>
+    <content_attribute id="violence-realistic">none</content_attribute>
+    <content_attribute id="violence-bloodshed">none</content_attribute>
+    <content_attribute id="violence-sexual">none</content_attribute>
+    <content_attribute id="violence-desecration">none</content_attribute>
+    <content_attribute id="violence-slavery">none</content_attribute>
+    <content_attribute id="violence-worship">none</content_attribute>
+    <content_attribute id="drugs-alcohol">none</content_attribute>
+    <content_attribute id="drugs-narcotics">none</content_attribute>
+    <content_attribute id="drugs-tobacco">none</content_attribute>
+    <content_attribute id="sex-nudity">none</content_attribute>
+    <content_attribute id="sex-themes">none</content_attribute>
+    <content_attribute id="sex-homosexuality">none</content_attribute>
+    <content_attribute id="sex-prostitution">none</content_attribute>
+    <content_attribute id="sex-adultery">none</content_attribute>
+    <content_attribute id="sex-appearance">none</content_attribute>
+    <content_attribute id="language-profanity">none</content_attribute>
+    <content_attribute id="language-humor">none</content_attribute>
+    <content_attribute id="language-discrimination">none</content_attribute>
+    <content_attribute id="social-chat">none</content_attribute>
+    <content_attribute id="social-info">none</content_attribute>
+    <content_attribute id="social-audio">none</content_attribute>
+    <content_attribute id="social-location">none</content_attribute>
+    <content_attribute id="social-contacts">none</content_attribute>
+    <content_attribute id="money-purchasing">none</content_attribute>
+    <content_attribute id="money-gambling">none</content_attribute>
+  </content_rating>
   <releases>
     <release version="1.0.0" date="2018-10-01">
       <description>