Git-ignore VIM temporary files (shader-slang#5047)

Following git-ignore rules are added to ignore VIM temporary files:
- *~: Ignores all files ending with a tilde (~), which are Vim's backup files.
- .*.swp: Ignores Vim swap files, which have .swp extension.
- .*.swo: Ignores Vim swap files created when a .swp file already exists.

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

.gitignore

@@ -86,3 +86,8 @@ vkd3d-proton.cache
 vkd3d-proton.cache.write
 *_d3d11.log
 *_dxgi.log
+
+# Vim temporary files
+*~
+.*.swp
+.*.swo