This is a core block and thus available by default in Gutenberg WordPress editor. No download required.
WordPress Heading Block in Gutenberg allows you to insert headlines ( h1 through h6 ). Headings are important for any content as it helps you structure your content. Headings make your content more readable to human and search engines.
Heading Block Features
From the toolbar options for the Heading block, you can select the heading tag H2, H3 or H4 (more in the sidebar settings). There are also basic formatting options in the block toolbar. You can also link the heading using the link option in the toolbar. In the block sidebar settings panel, it has options for all H1 to H6 level. It also has alignment options in the sidebar settings.
A simple title display using heading block on frontend.
This is how you can add headings in Gutenberg.
Heading block sidebar settings.