Add markdown.xml
Add markdown.xml

Brought to you by:
* Create 2008, Darrin Yeager. http://www.dyeager.org/
* Extended 2009, Claes Holmerson. http://github.com/claes/kate-markdown/

Slightly modified the XML
* Use proper formatting/indentation
* Add .markdown as extension, remove too generic .text

Fixed the missing kateversion attribute, used the latest version other XML
files were using (here: 3.7). Please fix if it is inappropriate.

REVIEW: 106455

cmacq2/kate,hlamer/kate,hlamer/kate,hlamer/kate,jfmcarreira/kate,sandsmark/kate,jfmcarreira/kate,cmacq2/kate,hlamer/kate,hlamer/kate,DickJ/kate,sandsmark/kate,hlamer/kate,hlamer/kate,sandsmark/kate,hlamer/kate,DickJ/kate,jfmcarreira/kate,DickJ/kate,hlamer/kate,DickJ/kate,cmacq2/kate,sandsmark/kate,hlamer/kate