The html output of the proof environemnt needs an extra space between `Proof.` and the proof body.
A minimal example:
```
:::{.proof}
See Appendix 1.
:::
```
![image](https://user-images.githubusercontent.com/16741954/152691167-39f20232-bb3c-44fc-a9ee-87b421dc5d17.png)

I am using v0.3.102.

2022-02-06T16:38:39Z
AlbertLei
closed
proof div: add one extra space in the HTML output
https://github.com/quarto-dev/quarto-cli/issues/314