added new dtutils library function find_image_by_id

content/lua.scripts.api.manual/dtutils/find_image_by_id.md

@@ -0,0 +1,31 @@
+---
+title: find_image_by_id
+id: find_image_by_id
+weight: 35
+draft: false
+author: "people"
+---
+
+## NAME
+
+find_image_by_id
+
+## SYNOPSIS
+
+look up an image by ID in the database
+
+## USAGE
+```
+local du = require "lib/dtutils"
+local img = du.find_image_by_id(imgid)
+```
+**imgid** - int - the image ID to retrieve  
+
+## DESCRIPTION
+
+**find_image_by_id** looks up an image by ID in the database.
+
+## RETURN VALUE
+
+**img** - _[dt_lua_image_t](../../../lua.api.manual/types/dt_lua_image_t.md)_ - image with the given ID if found, nil if not
+