Configure repo to not convert LF to CLRF on Windows

Git's default behavior is to convert LFs to CLRFs when checking out on Windows.
This breaks the tilde newline format directive as described here:
https://sourceforge.net/p/sbcl/mailman/sbcl-devel/thread/4D50C7E6.20400%40yv.org/#msg27025402

Also see
https://docs.github.com/en/get-started/getting-started-with-git/configuring-git-to-handle-line-endings
for details on configuring line endings in Git.

Author: kartik-s

.gitattributes

@@ -0,0 +1 @@
+*.lisp text eol=lf