Do not add carrage return to shell scripts (shader-slang#4811)

This commit prevents GIT from adding carrage return characters to shell
script files whose file extension is ".sh".

Currently git automatically adds a carrage return characters to all
lines in text files, which makes them Windows text file.
This causes a trouble when a shell script is submitted and it is ran on
WSL, because bash on WSL expects the script files in a unix text file
format.

Co-authored-by: Yong He <yonghe@outlook.com>

Author: jkwak-work

.gitattributes

@@ -1,2 +1,5 @@
 # indicate generated files so they don't appear in GitHub diffs
 *.slang.cpp linguist-generated
+
+# Set the line endings to LF for shell scripts
+*.sh text eol=lf