Template-based workspace initialization with `jp init`

When initializing a new workspace with jp init, currently we create a minimal default .jp directory.

I want to be able to use templates for jp init such that I can quickly scaffold a more complete set-up for my projects.

I'm thinking of a few required features:

• use jp init --template <template-name> to initialize with a given template name
• short-hand -t works as well
• templates are stored in $XDG_DATA_HOME/jp/templates/init/<template-name>
• files/folders in templates/init/<template-mame>/... are copied as-is to .jp/ on jp init
• multiple templates can be used by passing in --template more than once, any duplicate files are overwritten by the latest template flag
• if no --template flag is provided, but a default template exists in templates/init/, then it is used, unless --no-template is provided

See also: https://github.com/dcdpr/jp/issues/13#issuecomment-2953070665

Start by locating the jp init command and its existing minimal .jp initialization behavior, then review the linked issue discussion for context. Done means supporting repeated --template/-t flags, --no-template, the specified XDG template path, copying template contents with later templates overwriting duplicates, and default-template selection.