gitattributes: genesis, patches and vectors are byte streams, never line-ending converted

A Windows checkout was silently rewriting genesis.json to CRLF, so the
working-copy hash stopped matching the published and fleet hash, and the
package gate went red on a file whose bytes in git were correct. bd4f8b4
fixed this once by re-adding the file; this pins the rule so no checkout
can undo it again.

.gitattributes

@@ -0,0 +1,3 @@
+genesis.json -text
+patches/*.patch -text
+vectors/** -text