Convert README.txt to README.md and expand documentation

Problem/Motivation

The current module documentation is contained in a minimal README.txt file. The Drupal community has adopted README.md (Markdown) as the standard format for project documentation to provide better formatting and readability on Drupal.org and Git repositories.

Currently, the file lacks detailed instructions on installation, configuration, and usage.

Proposed resolution

1. Rename README.txt to README.md.
2. Rewrite the content using Markdown syntax.
3. Expand the documentation to follow the Drupal.org README.md template.
4. Include the following sections:
   • Introduction: Brief description of what the module does (adding soft hyphens to plain text fields like titles).
   • Requirements: List any dependencies (likely just Core).
   • Installation: Standard module installation steps.
   • Configuration:
     • Explain how to enable the feature on Content Types and Block Types.
     • Navigate to Structure > Content types > [Type] > Edit.
     • Navigate to Structure > Block layout > Custom block library > Block types > [Type] > Edit.
   • Usage:
     • Explain how the "Insert soft hyphen" button appears on entity forms.
     • Explain the visual highlighting of soft hyphens in the input field.
   • Maintainers: Current maintainer information.