docs: add GitHub Copilot CLI installation instructions

[GeekTrainer]

Adds GitHub Copilot CLI installation instructions to the README under the Specific MCP Clients section.

Changes

• Added "GitHub Copilot CLI" section after Cline
• Includes interactive setup (/mcp add) and manual configuration reference
• Links to the standard configuration section to avoid duplication
• Links to official Copilot CLI documentation

Testing

• Verified markdown renders correctly
• Internal link to standard configuration section is valid

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[GeekTrainer]

Question - would this fall under a small code exception since it's a small docs update, or will you need a CLA to be signed?

[RandomByte]

Thanks for the contribution.

It would be great if you could sign the CLA. It's possible that there is a pre-existing agreement between Microsoft and SAP regarding code contributions, you might need to consult your Open Source Program Office (or similar) for any questions regarding this.

[RandomByte]

Does the user also need to specify the name of the UI5 MCP server here?

[RandomByte]

I guess not, since it's an interactive flow as per https://docs.github.com/en/copilot/how-tos/copilot-cli/customize-copilot/add-mcp-servers#using-the-mcp-add-command

[flovogt]

@GeekTrainer Looking forward to incorporate your contribution into the repository. Could you please have another look at the comments?

[GeekTrainer]

@flovogt Sorry for the long delay here! It doesn't look like we already have a CLA agreement, and the process can be a bit complex. I am wondering if there's an exception available as it's a small docs update. If not I can work on pursuing the CLA signature.

[flovogt]

I don't mind to get the contribution done be our team. For me its more about #215 (comment)