gitattributes: keep LF in golden/test data files on Windows

The oakotio parity tests byte-compare serialized JSON against the
tests/data goldens; with only `* text=auto`, a Windows checkout hands
out CRLF and every round-trip assertion fails on the line endings
alone. Pin *.json and *.ove (XML) to eol=lf.

.gitattributes

@@ -6,3 +6,8 @@
 *.cpp      text eol=lf
 *.sh       text eol=lf
 *.desktop  text eol=lf
+
+# Golden/project data files are byte-compared by tests — keep LF on
+# Windows checkouts too (text=auto would hand out CRLF there).
+*.json     text eol=lf
+*.ove      text eol=lf