[Dataset page] Add filename/extension to download attribute

[tkohr]

PR adds filename/extension to download attribute for json and geojson files. Other file formats should have a name and don't need download attribute. Note that download attribute only takes effect on same-origin.

[f-necas]

Is the title retrieved from the data-api ? It could be used to set name of the file instead of data.

What append to let fileName = '' when it clicks on a csv format ?

[tkohr]

Is the title retrieved from the data-api ? It could be used to set name of the file instead of data.

Good point ! Completely forgot about that, added it now.

What append to let fileName = '' when it clicks on a csv format ?

Do you mean "why"? The download attribute does not seem to affect formats that cannot be opened by the browser. Filenames including extension behave already as expected in this case if I saw right, so I just keep it empty in this case.

[f-necas]

Hm, for me, if the format is, by example csv, it won't go through :

if (this.format === 'geojson') {
      completeFileName = `${fileName}.geojson`
    } else if (this.format === 'json') {
      completeFileName = `${fileName}.json`
    }

Then completeFileName will be empty.