patch 8.0.1764: lgtm considers tutor.es to be EcmaScript

Problem:    Lgtm considers tutor.es to be EcmaScript.
Solution:   Add a config file for lgtm. (Bas van Schaik, closes #2844)
diff --git a/Filelist b/Filelist
index 928d963..205c077 100644
--- a/Filelist
+++ b/Filelist
@@ -4,6 +4,7 @@
 # source files for all source archives
 SRC_ALL =	\
 		.hgignore \
+		.lgtm.yml \
 		.travis.yml \
 		appveyor.yml \
 		src/appveyor.bat \