migrated Github wiki links to readthedocs

doc/md/Plugin-System.md

@@ -49,10 +49,10 @@ hook_<plugin_name>_<hook_name>($data, $conf)
 
 Parameters:
 
-- data: see [$data section](https://github.com/shaarli/Shaarli/wiki/Plugin-System#plugins-data)
+- data: see [$data section](https://shaarli.readthedocs.io/en/master/Plugin-System/#plugins-data)
 - conf: the `ConfigManager` instance.
 
-For exemple, if my plugin want to add data to the header, this function is needed:
+For example, if my plugin want to add data to the header, this function is needed:
 
     hook_demo_plugin_render_header
 

doc/md/Plugins.md

@@ -72,4 +72,4 @@ Usage of each plugin is documented in it's README file:
 
 #### Third party plugins
 
-See [Community & related software](https://github.com/shaarli/Shaarli/wiki/Community-%26-Related-software#third-party-plugins)
+See [Community & related software](https://shaarli.readthedocs.io/en/master/Community-&-Related-software/)

doc/md/index.md

@@ -37,7 +37,7 @@ Login: `demo`; Password: `demo`
     - daily RSS feed
 - permalinks for easy reference
 - links can be public or private
-- extensible through [plugins](https://github.com/shaarli/Shaarli/wiki/Plugins#plugin-usage)
+- extensible through [plugins](https://shaarli.readthedocs.io/en/master/Plugins/#plugin-usage)
 
 ### Tag, view and search your links!
 - add a custom title and description to archived links