thunderbird: add page (#3054)

pages/common/thunderbird.md

@@ -0,0 +1,11 @@
+# thundebird
+
+> Email client and RSS reader.
+
+- Open thunderbird:
+
+`thunderbird`
+
+- Use a specific user profile directory:
+
+`thunderbird -P {{path/to/profile/directory}}`