docs: capitalize proper noun markdown (#10529)

lib/datasource/readme.md

@@ -17,7 +17,7 @@ The config contains:
 - `deprecationMessage`: a string description of the package's deprecation notice, if applicable
 - `sourceUrl`: a HTTP URL pointing to the source code (e.g. on GitHub)
 - `homepage`: a HTTP URL for the package's homepage. Ideally should be empty if the homepage and sourceUrl are the same
-- `changelogUrl`: a URL pointing to the package's Changelog (could be a markdown file, for example). If not present then Renovate will search the `sourceUrl` for a changelog file.
+- `changelogUrl`: a URL pointing to the package's Changelog (could be a Markdown file, for example). If not present then Renovate will search the `sourceUrl` for a changelog file.
 - `tags`: an object mapping tag -> version, e.g. `tags: { latest: '3.0.0' }`. This is only used by the `followTags` function.
 
 ## getDigest