Add LJ Speech dataset
Hey @anton-l,

Thanks a lot for the very clean integration!

1) I think we should now start having "automatic-speech-recognition" as a label in the dataset tagger (@yjernite is it easy to add?). But we can surely add this dataset with the tag you've added and then later change the label to `asr` 

2) That's perfect! Yeah good question - we're currently thinking about a better design with @lhoestq 

3) Again tagging @yjernite & @lhoestq here - guess we should add this license though! Thanks @anton-l for adding this one :)
About the points you mentioned:
1. Sure as soon as we've updated the tag sets in https://github.com/huggingface/datasets-tagging/blob/main/task_set.json, we can update the tags in this dataset card and also in the other audio dataset card.
2. For now we just try to have them as small as possible but we may switch to S3/LFS at one point indeed
3. If it's not part of the license set at https://github.com/huggingface/datasets-tagging/blob/main/license_set.json we can add it to this license set

For now it's ok to have the other-* tags but we'll update them very soon Let's merge this one and then we'll update the tags for the audio datasets. We'll probably also add something like this:
```
type:
- text
- audio
```

Thank you so much for adding this one, good job !
This PR adds the LJ Speech dataset (https://keithito.com/LJ-Speech-Dataset/)
As requested by #1841 
The ASR format is based on #1767 

There are a couple of quirks that should be addressed:
- I tagged this dataset as `other-other-automatic-speech-recognition` and `other-other-text-to-speech` (as classified by paperswithcode). Since the number of speech datasets is about to grow, maybe these categories should be added to the main list? 
- Similarly to #1767 this dataset uses only a single dummy sample to reduce the zip size (`wav`s are quite heavy). Is there a plan to allow LFS or S3 usage for dummy data in the repo?
- The dataset is distributed under the Public Domain license, which is not used anywhere else in the repo, AFAIK. Do you think Public Domain is worth adding to the tagger app as well?

Pinging @patrickvonplaten to review