Support embedding for Markdown files (.md, .markdown, etc.)

[seonghobae]

Currently, Markdown files (such as .md and .markdown) are explicitly excluded from the embedding and indexing pipeline in the kilocode project. As a result, documentation cannot be semantically searched or analyzed alongside source code.

Why this is important:
Many projects contain valuable information in Markdown documentation, including usage guides, design decisions, and API references. Enabling embedding and search for these files would greatly improve the utility and user experience of kilocode.

Suggested improvement:

• Include .md, .markdown, and possibly other common Markdown extensions (e.g., .mkd) in the embedding and indexing process.
• Allow semantic search over both code and documentation.

Reference:

• Related code: src/services/code-index/shared/supported-extensions.ts
• Currently, Markdown extensions are filtered out as follows:

  export const scannerExtensions = allExtensions.filter((ext) => ext !== ".md" && ext !== ".markdown")

Thank you for considering this enhancement!