Increase the indentation between line and the next heading

When using H3 headings, the text looks heavily glued together, which increases the cognitive load of identifying sections on the page.
![image](

The situation in Notion is slightly better, but far from ideal.
![image](

The same text in Confluence looks readable much better.
![image](


It turns out that now, to improve readability, you either have to use large headings or add a blank line between sections, which is inconvenient and would be better to add some spacing between sections.