fix(builtin): add transitive typings to runfiles provider produced by js_library

[mattem]

Add transitive typings to runfiles provider produced by js_library. Allows downstream consumers that require the .d.ts files at runtime (eg typechecking) to access the files via the runfiles tree.

[alexeagle]

I'm surprised this is useful, what's the use case? a typescript program deps on a binary and wants to typecheck against some library code contained in that binary?

[mattem]

Yeah, internally running tsc_test to perform typechecking, where one of the dependencies is via a js_library which outputs the required .d.ts files. There is an alternative method, js_library outputs types to an output group types, so it's possible to do:

filegroup(
    name = "types_dts",
    srcs = [
        "//some:js_library"
    ],
    output_group = "types",
)

tsc_test(
    name = "typecheck",
    args = [
        "--noEmit",
        "--incremental",
        "false",
    ],
    chdir = package_name(),
    data = [
        ":types_dts",
        ...
    ],
)

[mattem]

//examples:examples_protobufjs flake