main: Add .gitattributes

This change ensures that devs using Windows:
1. will avoid accidentally pushing modified files with CRLF line endings
(i.e. this repo will maintain a consistent use of LF line endings)
2. won't see files as modified in git due to line ending changes
3. can still use CRLF in their working trees.

This file explicitly declares the files which should be treated like
text, which means that git won't incorrectly try to modify line endings
on a binary file.

.gitattributes

@@ -0,0 +1,18 @@
+# Normalize line endings of text files to LF regardless of OS or git settings
+*.conf          text
+*.dockerignore  text
+.gitattributes  text
+.gitignore      text
+*.go            text
+*.gv            text
+*.json          text
+*.md            text
+*.mediawiki     text
+*.mod           text
+*.py            text
+*.service       text
+*.sh            text
+*.sum           text
+*.svg           text
+*.xml           text
+*.yml           text