chore: deprecate markdown_quill export, ignore warnings

[EchoEllet]

Description

Deprecate markdown_quill.dart export as support for markdown conversation has been discounted (#1997).

It seems that we have deprecated DeltaX completely and related packages but didn't deprecate the file markdown_quill.dart. We should give users more time before introducing a breaking change.

There was questions about this API in Slack and it was confusing to the user since the project no longer has plan to keep the experimental support for those methods, we should be able to remove them since they are experimental but for this file, it wasn't clear enough.

The quill_markdown (from lib/src/packages/quill_markdown) is a local copy of quill_markdown. There were some bug fixes made in our local changes and did plan on sending them to the upstream repo before completely removing this package from the project however it seems that this package is no longer maintained.

Related Issues

• Related chore: drop support for HTML, PDF, and Markdown converting functions #1997

Type of Change

• ✨ New feature: Adds new functionality without breaking existing features.
• 🛠️ Bug fix: Resolves an issue without altering current behavior.
• 🧹 Code refactor: Code restructuring that does not affect behavior.
• ❌ Breaking change: Alters existing functionality and requires updates.
• 🧪 Tests: Adds new tests or modifies existing tests.
• 📝 Documentation: Updates or additions to documentation.
• 🗑️ Chore: Routine tasks, or maintenance.
• ✅ Build configuration change: Changes to build or deploy processes.