Copy two existing blog posts from content/posts/ (old Gatsby location)
to src/content/posts/ with updated frontmatter:
- localize-react-without-bloating-the-bundle.md
- speeding-up-webpack-typescript-incremental-builds-by-7x.md (was .mdx)
Frontmatter changes: removed path/heroImage fields, added type/tags/summary,
simplified date to YYYY-MM-DD format. Body content preserved verbatim.
Ken