Added ps dependency to Dockerfile (TryGhost#21471)

no issue

- When stopping `yarn dev` with ctrl+c in the dev container, you'd get
an error because the container doens't have `ps` installed, which is
used by node under the hood. Adding this dependency fixed the error so
`yarn dev` (and other commands) exit cleanly

.devcontainer/.docker/Dockerfile

@@ -21,6 +21,7 @@ RUN curl -s https://packages.stripe.dev/api/security/keypair/stripe-cli-gpg/publ
         git \
         stripe \
         zsh \
+        procps \
         default-mysql-client && \
     npx -y playwright@1.46.1 install --with-deps