Update runtime files

runtime/ftplugin/gdshader.vim

@@ -0,0 +1,12 @@
+vim9script
+
+# Vim filetype plugin file
+# Language: Godot shading language
+# Maintainer: Maxim Kim <habamax@gmail.com>
+
+if exists("b:did_ftplugin") | finish | endif
+b:did_ftplugin = 1
+
+b:undo_ftplugin = 'setlocal suffixesadd<'
+
+setlocal suffixesadd=.gdshader