Specify the repository in Cargo.toml

Summary: This enables crates.io and docs.rs to show a link to the repository.

Reviewed By: alanz

Differential Revision: D51044872

fbshipit-source-id: 4cf84fea028fa27fff310ece88f1d8594db20b81

Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 categories = ["parsing", "text-editors"]
 description = "erlang grammar for the tree-sitter parsing library"
+repository = "https://github.com/WhatsApp/tree-sitter-erlang"
 edition = "2018"
 keywords = ["incremental", "parsing", "erlang"]
 license = "MIT"