[geary] Add contribution guide

[Michael Gratton <mjog src gnome org>]

commit c43d86f35a840bdc56753676d5d54550bf70b744
Author: Michael Gratton <mike vee net>
Date:   Wed Aug 1 05:28:08 2018 +0000

    Add contribution guide

 CONTRIBUTING.md | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 00000000..9afa680d
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+++ b/CONTRIBUTING.md
@@ -0,0 +1,10 @@
+Contribute to Geary
+-------------------
+
+Want to help improve Geary? There are a number of ways you can contribute:
+
+ * [Bug Reporting](https://wiki.gnome.org/Apps/Geary/ReportingABug)—report new bugs or request new features
+ * [User Experience Design](https://wiki.gnome.org/Apps/Geary/Design)—research and develop Geary’s user 
experience
+ * [Development](https://wiki.gnome.org/Apps/Geary/Development)—fix bugs and add new features
+ * [Translating](https://wiki.gnome.org/Apps/Geary/Translating)—translate Geary’s user interface and user 
manual into new languages
+ * [Join the discussion](https://wiki.gnome.org/Apps/Geary/Contact) on the mailing list or IRC channel