Implement 'list' command to display releases, marking installed and stable versions

[piraz]

Overview

Implement the list command for nvimm.

This command should:

• Fetch all available releases (for example, via GitHub API or repository backend).
• List every release to the client/user.
• Display installed releases and available releases separately.
• Clearly indicate which release is the stable version by labeling it as "stable".

Requirements

• Use reliable release fetching (query GitHub releases endpoint or equivalent).
• Display formatting should make it clear which versions are installed and which is stable.
• Mark selected release with * next to them in the output.
• Mark the stable version with "stable" next to its version string.
• If a release is both installed and stable, ensure both markers are visible.
• Documentation must be in English by default as per chat convention.

Example Output

Installed versions
* 0.11.5 (stable)
  0.11.4
  0.11.3
  0.11.2
  0.10.4

Available versions
  nightly
  0.11.1
  0.11.0
  0.10.3
  0.10.2
  0.10.1
  0.10.0
  0.9.5
  0.9.4
  0.9.2
  0.9.1
  0.9.0
 .
 .
 .

Extensibility

• Structure the solution for future expansion (extra metadata, filtering, etc.).