chore(repo): pin LF line endings via .gitattributes

Prevents accidental CRLF rewrites of the entire tree on Windows
checkouts or by editors that flip endings on save. Anvil is a
Linux-first Rust crate with no Windows-native scripts, so a single
LF policy keeps diffs free of phantom whole-tree churn.

Author: UnbreakableMJ

.gitattributes

@@ -0,0 +1,4 @@
+# Normalize all text files to LF in the repo and on checkout.
+# Anvil is a Linux-first Rust crate with no Windows-native scripts,
+# so a single line-ending policy keeps diffs clean across platforms.
+* text=auto eol=lf