Add host and port configuration

[holkerveen]

What it does

This PR is for including host and port configuration to the example/standalone server start script, as well as to the standalone frontend app. Defaults are specified such that original operation should be unchanged.

I opted to parse the relevant command line arguments myself as opposed to with a library, because I felt it is a bit of overkill to introduce an extra dependency for parsing command line arguments.

closes eclipse-glsp/glsp#1410

How to test

From the examples/workflow-standalone dir, start the example server with something like yarn ts-node scripts/start-example-server.ts --port 1234 --host 127.0.0.1 or similar, and build the frontend app with GLSP_SERVER_PORT=1234 GLSP_SERVER_HOST=127.0.0.1 yarn build.

The server should listen on the port and host specified, and the frontend should attempt to connect to the same.
Observe that default configuration has not changed

Follow-ups

Changelog

• This PR should be mentioned in the changelog
• This PR introduces a breaking change (if yes, provide more details below for the changelog and the migration guide)

[holkerveen]

Hi there! I did complete the ECA and could validate by entering my username in the ECA Validation Tool. I don't know how to re-check though

[tortmayr]

Thanks. LGTM 👍🏼

I retriggered the ECA check and now everything passes.