Treat *.ml{i} in Linguist as OCaml

Author: kevinji

.gitattributes

@@ -14,3 +14,5 @@ frontend/website/static/*.bc.js filter=lfs diff=lfs merge=lfs -text
 src/app/archive/archive_graphql_schema.json linguist-generated=true
 docs/res/block_production_fsm.dot.png filter=lfs diff=lfs merge=lfs -text
 rfcs/res/hard-fork-package-generation-buildkite-pipeline.dot.png filter=lfs diff=lfs merge=lfs -text
+*.ml linguist-language=OCaml
+*.mli linguist-language=OCaml