Added documentation for dev mode

[cicalese]

Document the new development mode features for Canasta CLI:

• Creating dev mode installations with --dev flag
• Specifying image tags with --dev-tag
• Building from local source with --build-from
  • Canasta/ (required)
  • CanastaBase/ (optional)
  • Canasta-DockerCompose/ (optional)
• Enabling/disabling dev mode on existing installations
• IDE setup for VSCode and PHPStorm
• Xdebug trigger configuration (cookies for browser, env vars for CLI)
• Directory structure and log locations
• Troubleshooting guide
• Command reference for create, start, and restart

Also document running Canasta on non-standard ports:

• Configuring HTTP_PORT and HTTPS_PORT in .env
• Including port in domain name and wikis.yaml
• Example: running two wiki farms on the same server

Related PRs:

• Add dev mode to CLI Canasta-CLI#140
• Fix symlink creation for mounted directories CanastaBase#54
• Support overriding base image via build arg Canasta#571
• Use CANASTA_IMAGE environment variable for web service image Canasta-DockerCompose#73
• Added documentation for dev mode #22

[yaronkoren]

This looks great!