Select all specifications

[yeekangc]

Provide an option for users to select all specifications

I didn't see this in the release currently available?

[kathrynkodama]

There is a built in VS Code select all option. We looked into having the select all selected by default but have not determined how to do that yet.

[rzgry]

We can default to selecting all specifications by adding picked: true here https://github.com/MicroShed/mp-starter-vscode-ext/blob/master/src/util/vscodePrompts.ts#L122

See QuickPickItem documentation: https://code.visualstudio.com/api/references/vscode-api#QuickPickItem

Would also be good to add a configuration setting to allow users to pick the default behaviour (default to all specs selected or none selected). (This can be done in 1 PR or as a follow up). https://code.visualstudio.com/api/references/contribution-points#contributes.configuration