Clarify the location of md files for Copilot Chat customization within user profiles

[CraftyCraftress]

This change clarifies:

• That md files for customizing Copilot Chat need to go in the prompts sub-directory of a profile.
• Clarifies where files associated with the default profile are stored.

[ntrogh]

@CraftyCraftress We don't include this information as we don't recommend users create those files directly in their user profile. The location of the files in the user profile might be subject to change.

[CraftyCraftress]

@CraftyCraftress We don't include this information as we don't recommend users create those files directly in their user profile. The location of the files in the user profile might be subject to change.

@ntrogh What is the suggested way to create & sync prompts/instructions across machines that are not repo/workspace specific?

[ntrogh]

@CraftyCraftress When you create a prompt/instructions file (Chat: New Prompt File or Chat: New Instructions File), you can choose between workspace or user profile.

For user-profile prompts or instructions, they are subject to settings sync, so will roam with you across machines.