update docs

[ecarreras]

This pull request enhances the documentation for single-value indicator graphs by adding details about new display options and providing practical usage examples. The changes clarify how to configure indicators with progress bars, percentage displays, suffixes, and conditional formatting, making it easier for users to understand and implement these features.

Documentation improvements for indicator graph configuration:

• Expanded the list of indicator graph attributes in docs/api-reference.md to include progressbar, show_percent, suffix, color, icon, and total_domain, with clear explanations for each option.
• Updated the indicator graph method documentation to describe the new process(value, total=0) method, detailing its parameters and the structure of its return value, including support for progress bar and percentage display.

Usage and example enhancements:

• Added practical code examples in docs/examples.md demonstrating how to use indicator graphs with progress bars and percentage displays, showing expected output for each scenario.
• Improved the usage guide in docs/usage.md by including sample code for indicators with progress bars and percentage displays, and listing all relevant indicator attributes for quick reference.