chore: add dev-container readme

src/dev-container/README.md

@@ -0,0 +1,24 @@
+# Dev Container
+
+This package houses the dev-container image.
+
+It includes:
+
+- go (1.15.2)
+- bazel (latest via bazelisk)
+- node (latest lts via nvm)
+
+As well as any other tooling within VSCode Dev Containers.
+
+## Building
+
+To build and use locally,
+
+```sh
+bazel run //srv/dev-container && docker run -it --rm bazel/src/dev-container:dev-container
+```
+
+To just use, this is published to two registries. There is no effective difference, except that GitHub's registry requires login, and Docker Hub does not.
+
+- `docker pull roleypoly/dev-container:main`
+- `docker pull docker.pkg.github.com/roleypoly/roleypoly/dev-container:main`