Improve Markdown syntax in Document (#12949)

* Use GitLab instead of Gitlab

Only change text part, the Alert.Transport.Gitlab class left as is.

* Fix href in document

* Move section in document

The agent list in this document is sorted by alphabetical order,
"SDFS info" is the only exception.

* Remove trailing spaces in document

* Align code in document

* Fix Markdown in document

- Escape underline
- Add syntax highlight
- Add two space in the end of line to make it a newline
- Add newline before list or code section

* Update LibreNMS/Alert/Transport/Gitlab.php

Co-authored-by: Jellyfrog <[email protected]>

doc/API/Devices.md

@@ -1310,7 +1310,7 @@ search all oxidized device configs for a string.
 Route: `api/v0/oxidized/config/search/:searchstring`
 
   - searchstring is the specific string you would like to search for.
-  
+
 Input:
 
 -
@@ -1345,7 +1345,7 @@ Returns a specific device's config from oxidized.
 Route: `api/v0/oxidized/config/:device_name`
 
   - device_name is the full dns name of the device used when adding the device to librenms.
-  
+
 Input:
 
 -

doc/API/Inventory.md

@@ -11,7 +11,7 @@ cage, then the sfp itself. The way this API call is designed is to
 enable a recursive lookup. The first call will retrieve the root
 entry, included within this response will be entPhysicalIndex, you can
 then call for entPhysicalContainedIn which will then return the next
-layer of results.  To retrieve all items together, see 
+layer of results.  To retrieve all items together, see
 [get_inventory_for_device](#get_inventory_for_device).
 
 Route: `/api/v0/inventory/:hostname`
@@ -69,8 +69,8 @@ Output:
 
 ### `get_inventory_for_device`
 
-Retrieve the flattened inventory for a device.  This retrieves all 
-inventory items for a device regardless of their structure, and may be 
+Retrieve the flattened inventory for a device.  This retrieves all
+inventory items for a device regardless of their structure, and may be
 more useful for devices with with nested components.
 
 Route: `/api/v0/inventory/:hostname/all`
@@ -114,4 +114,4 @@ Output:
         }
     ]
 }
-```
+```