gedit: Add highlighting for gedit

Added a gtksourceview syntax highlighting file for conky configs.
Everything is explained in the README.md

extras/gedit/README.md

@@ -0,0 +1,31 @@
+# Gedit syntax highlighting
+
+Note this is purely a highlighting **NOT** a syntax validator, the highlighting may not be 100% correct and not all arguments or keywords may be recognised properly. Feel free to change a regex if you have got a better one.
+
+The syntax highlighting will automatically be applied to all files with `conky` in their name. eg. `my_config.conky` (unfortunately it also triggers for the conky.lang file itself, you should set it to XML manually)
+
+ *  [Gedit Syntax Highlight documentation](https://developer.gnome.org/gtksourceview/stable/lang-reference.html)
+ * [Regex Tutorial](http://www.rexegg.com/)
+ * [Regex Testing](https://regex101.com/)
+
+Developers: if you want to add a new keyword just add it (in order) to the list. In `keywordsConfig` for config keywords and in `keywordsText` for variables. If it has a number at the end, eg `color1` just use `color[0-9]{1}` if the number is mendatory or `color[0-9]?` if it is not.
+
+If you want to add your own group of argument keywords you can look at the current definitions and copy them, should be self explainatory.
+
+***
+
+ for medit v1.1.1:
+` /usr/share/medit/language-specs/conky.lang`
+
+ for medit - older versions:
+ `/usr/share/medit-1/language-specs/conky.lang`
+
+ for gedit v2.x
+` /usr/share/gtksourceview-2.0/language-specs/conky.lang`
+ or (for single user)
+` ~/.local/share/gtksourceview-2.0/language-specs/conky.lang`
+
+ for gedit v3.x
+` /usr/share/gtksourceview-3.0/language-specs/conky.lang`
+ or (for single user)
+` ~/.local/share/gtksourceview-3.0/language-specs/conky.lang`