feat: add support for launching tryptich in specific directory

[dladukedev]

As a user, I would like the ability to launch Triptych with a specific directory selected instead of always launching in the current directory. This is useful for facilitating several workflows including creating a shortcut to a specific folder or jumping to another location within the file tree while working.

Changes

• feat: Add support for argument to Triptych user command that opens Triptych in the specified
• fix: correct directory check, replace not vim.fn.isdirectory(dir) with vim.fn.isdirectory(dir) == 0

Options Considered

Add args option to existing Triptych command (This PR)

• Pros
  • Very few code changes required to implement
  • Uses existing flow, only now exposed to external users
• Cons
  • Unclear what Triptych ~/MyDirectory should do if Triptych is already open, especially if "~/MyDirectory" is not the currently focused directory -- Currently just closes Triptych like the current command

Update to 3 user commands, Triptych(Toggle), TriptychOpen, TriptychClose with only TriptychOpen accepting a directory

• Pros
  • Removes ambiguity of how Tryiptych ~/MyDirectory should act if Triptych is already open
  • Allows possibility of supporting calls to TryptichOpen while Tryptich is already open for quick navigation
• Cons
  • Increases API support surface area
  • Unclear how easy it would be to implement the flow

[simonmclean]

Nice one, thanks!