djot-0.1.0.0: test/super_subscript.test

```
H~2~O
.
<p>H<sub>2</sub>O</p>
```

```
mc^2^
.
<p>mc<sup>2</sup></p>
```

```
test^of superscript ~with subscript~^
.
<p>test<sup>of superscript <sub>with subscript</sub></sup></p>
```

```
H{~2 ~}O
.
<p>H<sub>2 </sub>O</p>
```