docs(framework) Update how to configure clients

[WilliamLindskog]

Issue

Outdated documentation for how-to-configure-clients.

Description

Added example using ServerApp instead of start_server. Also checked for typos and other small things.

Related issues/PRs

Proposal

Explanation

Checklist

• [x] Implement proposed change
• [x] Write tests
• [x] Update documentation
• [x] Make CI checks pass
• [ ] Ping maintainers on Slack (channel #contributions)

Any other comments?

[WilliamLindskog]

@jafermarq added lines for your comment