Compute coverage stats

### Description of feature

In the [_Summary/detail_ view](https://blobtoolkit.genomehubs.org/view/Dilophus/dataset/idDilFebr1_1/detail?yField=ERR10841320_cov#Summary), one can see:

| | | |
|-|-|-|
| Reads | PACBIO_SMRT (undefined) | ERR10841320 (cov: NaN) |

It'd be nice to compute the coverage (total read length divided by genome size ?) and sort out the "undefined" as well.