feat: keep measurement records in measurements/

The seven core probe records move from Abdess/retrobios-measurements at
75e878143687 into this repository, copied byte for byte: one .jsonl per
emulator and a gzip data file per record. merge=union lets two branches
that each add a line merge.

.gitattributes

@@ -21,3 +21,9 @@ install.ps1 text eol=lf
 # preserved, so they follow the LF rule above.
 bios/** -text
 data/** -text
+
+# Measurement records are append-only: two branches that each add a line to
+# the same file merge by keeping both. A data file is bytes its line vouches
+# for by sha256.
+measurements/*.jsonl text eol=lf merge=union
+measurements/data/** -text