Speaking in Spanish about `intent=':unit'` is not entirely correct

First of all, thank you very much for your contribution. Thanks to the LaTeX team for adding the `\MathMLintent` command, I can now test several things, including the units of measurement I commonly use.

I developed the test using [MathCATDemo](https://daisy.github.io/MathCATDemo/) and Firefox (I'm not using NVDA for now), I'll focus on using $$1 \mathrm{km}^2$$ as a base example which generates the following output:

```xml

```

When using SimpleSpeak/Terse/Medium the output is correct:

```
1 kilómetro al cuadrado
```

But when switching to SimpleSpeak/Verbose, the output is:

```
1 kilómetro elevado al cuadrado
```

which is incorrect in Spanish and should say:

```
1 kilómetro elevado a 2
```

When using ClearSpeak/Terse/Medium/Verbose the output is correct:

```
1 kilómetro cuadrado
```

But in Spanish, `1` is singular and `0`, `2`, `3`, etc. are plural, so an `s` must be added to the word `cuadrado`. If I modify the example to:

```xml

```
Using ClearSpeak/Terse/Medium/Verbose the output is:

```
2 kilómetros cuadrado
```

and the correct thing would be:

```
2 kilómetros cuadrados
```

The same applies to the rest of the units of measurement that I provided. Now, if we modify the input to $$1 \mathrm{km}^3$$:

```xml

```

When using SimpleSpeak/Terse/Medium/Verbose the output is:

```
1 kilómetro cúbica
```
Which is incorrect and in Spanish (Terse/Medium) and the correct one (maintaining the output style provided by $$\mathrm{km}^2$$) it should say:

```
1 kilómetro al cubo
```

and (Verbose)

```
1 kilómetro elevado a 3
```

Using ClearSpeak/Terse/Medium/Verbose the output is:

```
1 kilómetro al cubo
```

and it should be (maintaining the output style provided by $$\mathrm{km}^2$$):

```
1 kilómetro cúbico
```

And considering that 1 is singular and 0, 2, 3, etc. are plural, then it must be modified a little ($$2 \mathrm{km}^3$$):

```
2 kilómetros cúbicos
```

To summarize, the reading could be standardized (same style) for $$\mathrm{km}^2$$ and $$\mathrm{km}^3$$, and also (I think) SimpleSpeak/Terse should be equal to ClearSpeak in this case.

With higher-order powers (4, 5, ...) the issue is similar and the reading sounds a bit strange, I will modify the example to $$\mathrm{km}^4$$:

```xml

```

When using ClearSpeak/Terse/Medium/Verbose the output is:

```
1 kilómetro a la cuarto potencia
```
Which is incorrect (it should say "cuarta" not "cuarto") and sounds quite strange. It's natural that he would say:

```
1 kilómetro a la cuarta
```
or

```
1 kilómetro elevado a 4
```

When using SimpleSpeak/Terse/Medium/Verbose the output is:

```
1 kilómetro a la cuarto
```

Which again is wrong, for SimpleSpeak/Terse/Medium, It's natural that he would say:

```
1 kilómetro a la cuarta
```
or

```
1 kilómetro elevado a 4
```

and for SimpleSpeak/Verbose say:

```
1 kilómetro elevado a la cuarta potencia
```

However, using "cuarta potencia, quinta potencia, sexta potencia,..." is not common and "elevado a ..." is preferred.

I hope this report is helpful...Thanks again