Setup a new v8-poc package

This is a new package that depends on rusty-v8 for embedding a v8
engine.  This builds and works on non-musl platforms now because
rusty-v8 provides versions for that.  But we mocked out the loading of
a musl built library.

TODO: iterate on providing the musl built version for musl-linux builds.
TODO: create a release workflow for publishing the artifact that rusty-v8 can link against

codex-rs/v8-poc/BUILD.bazel

@@ -0,0 +1,12 @@
+load("//:defs.bzl", "codex_rust_crate")
+
+codex_rust_crate(
+    name = "v8-poc",
+    crate_name = "codex_v8_poc",
+)
+
+codex_rust_crate(
+    name = "v8-poc-rusty-v8",
+    crate_features = ["rusty_v8"],
+    crate_name = "codex_v8_poc",
+)