Monorepo for Tangled

git: add gitattributes to mark generated files

both jj-vcs and tangled don't support gitattributes yet, but this would
be still valuable.

Signed-off-by: Seongmin Lee <git@boltless.me>

boltless.me 117828b6 0f6d3ee0

verified
+1
+1
.gitattributes
··· 1 + api/tangled/** linguist-generated -diff