Updates to J-Link description

[jreineckearm]

Fixes

• [Feature Request]: J-Link debug settings vscode-cmsis-debugger#617

Changes

• Updates J-Link telnet description.
• Adds extended settings docs for J-Link (connect mode, reset).

Not added yet: Switch between semihosting and RTT. At the moment Telnet is always semihosting.

Checklist

• 🤖 This change is covered by unit tests (if applicable).
• 🤹 Manual testing has been performed (if necessary).
• 🛡️ Security impacts have been considered (if relevant).
• 📖 Documentation updates are complete (if required).
• 🧠 Third-party dependencies and TPIP updated (if required).

[jreineckearm]

Early eyes are welcomed: @RobertRostohar , @jkrech , @ReinhardKeil :

• Still need to implement/verify connect and reset, hence a draft.

[jkrech]

Look plausible to me, given the capabilities provided by J-Link Server

[jreineckearm]

Template PR here: Open-CMSIS-Pack/debug-adapter-registry#82

[jreineckearm]

Remaining gap for telnet: switch between semihosting and RTT. To be addressed separately to get the big change out of the way.

[jkrech]

I do not have the bandwidth to review this for technical implications.