patch 8.2.0105: Vim license not easy to find on github

Problem:    Vim license not easy to find on github.
Solution:   Add a separate LICENCE file. (closes #5458)
diff --git a/Filelist b/Filelist
index ca72742..6ebb3f7 100644
--- a/Filelist
+++ b/Filelist
@@ -652,6 +652,7 @@
 RT_ALL =	\
 		README.txt \
 		README.md \
+		LICENSE \
 		CONTRIBUTING.md \
 		runtime/bugreport.vim \
 		runtime/doc/*.awk \