chore: pin shipped text formats to LF

This repository's drivers are shell scripts executed on Linux accelerator
hosts, and its consumers record the SHA-256 of the files they ran. With Git's
default autocrlf on Windows a checkout rewrites those files with CRLF, which
breaks the shell drivers outright and changes every digest a receipt refers to.

.gitattributes

@@ -0,0 +1,12 @@
+# Everything here runs on Linux accelerator hosts, and campaign receipts record
+# the SHA-256 of the harness files they were produced by. A CRLF checkout on
+# Windows would both break the shell drivers and change every recorded digest,
+# so pin the text formats this repository ships.
+*.py text eol=lf
+*.sh text eol=lf
+*.json text eol=lf
+*.yaml text eol=lf
+*.csv text eol=lf
+*.tsv text eol=lf
+*.txt text eol=lf
+*.md text eol=lf