runtime(kivy): update kivy syntax, include ftplugin

Kivy uses "#:" for preprocessing commands (like "#:import ...") which
were overridden by the comment syntax. This has been changed, and a
commentstring has been added.

closes: #15163

Signed-off-by: Riley Bruins <ribru17@hotmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/MAINTAINERS b/.github/MAINTAINERS
index 2b4c475..3200905 100644
--- a/.github/MAINTAINERS
+++ b/.github/MAINTAINERS
@@ -180,6 +180,7 @@
 runtime/ftplugin/jq.vim	    	        @vito-c
 runtime/ftplugin/kconfig.vim		@chrisbra
 runtime/ftplugin/kdl.vim		@imsnif @jiangyinzuo
+runtime/ftplugin/kivy.vim		@ribru17
 runtime/ftplugin/kotlin.vim		@udalov
 runtime/ftplugin/less.vim		@genoma
 runtime/ftplugin/liquid.vim		@tpope