chore: add .gitattributes and normalize line endings to LF

.gitattributes

@@ -0,0 +1,18 @@
+# Normalize all text files to LF in the repository and on checkout.
+# Stops the "LF will be replaced by CRLF" churn on Windows.
+* text=auto eol=lf
+
+# Binary assets — never normalize or diff as text.
+*.png   binary
+*.jpg   binary
+*.jpeg  binary
+*.gif   binary
+*.ico   binary
+*.webp  binary
+*.wasm  binary
+*.ttf   binary
+*.otf   binary
+*.woff  binary
+*.woff2 binary
+*.tgz   binary
+*.pdf   binary