add github templates

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

.github/ISSUE_TEMPLATE.md

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+
+### General informations
+
+- OfflineIMAP version:
+- server name or domain:
+- CLI options:
+- configuration (remove private data):
+```
+<configuration goes here>
+```
+
+### Log error
+
+```
+<error goes here>
+```
+
+### Step to reproduce the error

.github/PULL_REQUEST_TEMPLATE.md

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+
+> Add character x.
+
+- [] I've read the [DCO](http://www.offlineimap.org/doc/dco.html).
+- [] I've read the [Coding Guidelines](http://www.offlineimap.org/doc/CodingGuidelines.html)
+- [] The relevant informations about the changes stands in the commit message, not here.
+- [] Code changes follow the style of the files they change.
+- [] Code is tested (provide details).
+
+### References
+
+- Bug: #no_space
+