Docs: Get title of the document from the markdown content header

Currently, the title of the page is using the file path for the related page. For example, when this page being rendered, the title become as follow:

For this case, it would be better to set the title as Getting-Started-with-the-MAUI. Therefore, we can try to get the h1 header from the content and use it as the title if it exists, otherwise, we can use the current approach and use and normalize the file path and use it as the title.

No implementation files or tests are named. Start by tracing how a Markdown page's title is currently derived from its file path, then locate the rendering or title-generation entry point and related tests. Done means an H1 supplies the title when present, while pages without one retain the normalized file-path fallback.