Normalize tsx line endings, add explanation

.gitattributes

@@ -4,7 +4,10 @@
 # Explicitly declare text files we want to always be normalized and converted
 # to native line endings on checkout.
 *.rs text
+
+# Normalize example TMX & TSX file line endings for consistent tests among all platforms.
 *.tmx text eol=crlf
+*.tsx text eol=crlf
 
 # Denote all files that are truly binary and should not be modified.
 *.png binary