Add solid_queue_monitor as a Recommended Monitoring Option in Readme file

[vishaltps]

Overview

This PR adds solid_queue_monitor as a recommended monitoring solution for Solid Queue, with particular emphasis on its benefits for Rails API-only applications and projects requiring minimal dependencies.

Changes

• Added a dedicated "Monitoring" section to the table of contents
• Created a comprehensive Monitoring section that showcases both monitoring options:
  • solid_queue_monitor: Positioned as the first option, highlighting its zero-dependency nature and suitability for API-only applications
  • mission_control-jobs: Maintained as the officially supported dashboard with its comprehensive feature set
• Added a reference to solid_queue_monitor in the "Failed jobs and retries" section as an alternative to mission_control-jobs

Motivation

While mission_control-jobs is the officially supported monitoring solution, it may not be the best fit for all applications, particularly:

• Rails API-only applications where adding Rails views/assets dependencies is unnecessary
• Projects where a lightweight, zero-dependency solution is preferred
• Applications where a simpler UI with core monitoring features is sufficient

The solid_queue_monitor gem fulfills these needs while offering all essential monitoring features, making it an excellent complement to the existing mission_control-jobs option.

Benefits

This change improves the documentation by:

• Providing options that cater to different application architectures and requirements
• Helping developers make informed choices about monitoring tools based on their specific needs
• Highlighting community contributions that enhance the Solid Queue ecosystem

By offering multiple monitoring options, we accommodate different user preferences and application constraints, making Solid Queue more versatile and accessible.

[rosa]

Hey @vishaltps, thanks for this, and thanks for your work on solid_queue_monitor!
Currently, I'm not comfortable recommending an option to manage jobs (as the first option, also) over which I have no control and that uses private APIs (basically going to low-level SQ data structures) that can change at any moment, as it could cause problems I wouldn't be best equipped to help with.

Just a note: Mission Control can be used by API-only apps so that shouldn't be a blocker for people running one of such apps.