Add devcontainer

[NicoZweifel]

I was trying to run the tests in a docker container and ended up with this devcontainer after
having some fun with deno-puppeteer.

lucacasonato/deno-puppeteer/pull/70
lucacasonato/deno-puppeteer/pull/71

The dependencies in the Dockerfile there are pretty much the same and it could be reused as a base image (tested locally):

ARG DENO_VERSION=1.28.2
FROM denoland/puppeteer:$DENO_VERSION

WORKDIR /app

COPY . .

RUN  deno cache --no-check --import-map=./www/import_map.json src/dev/deps.ts src/server/deps.ts www/main.ts

# Set DENO_DEPLOYMENT_ID
RUN /bin/bash -l -c 'echo export DENO_DEPLOYMENT_ID=$"(git rev-parse HEAD)" > /etc/profile.d/docker_init.sh'

EXPOSE 8000

CMD ["task", "test"]

[Mrashes]

This PR is pretty stale, could we close @NicoZweifel ?