[Feature Request] Add percentage to progress bar

[datadecoded]

Adding a percentage and message count to the import or export process progress bar to give an idea of how long it takes to finish would be helpful. The percentage (50%) would be on side of the bar and the message count would be on the other side of the bar (50/100). Thanks!

[tmo1]

Exporting already displays both the number of messages already exported and the total number present on the system. Importing does not, due to an architectural limitation of the app as currently designed: since we read the (ND)JSON line by line, we don't know how many messages it contains until we're done.

A solution would be to include some metadata in the ZIP file. I'd like to do that for the next file format update, but those are rare, to avoid breaking backward compatibliity.