Warn when accidentally saving just lines, etc.

[jidanni]

Description

Find some road,

• highway=unclassified
• oneway=no

and remove the

• highway=unclassified

tag by accident, and save your changes.

No warning is given that all there is is a "line" left on the map.

[k-yle]

This would be trivial to implement, oneway just needs to be added to onlyAttributeKeys:

iD/modules/validations/missing_tag.js

Line 12 in 9cd1ed4

var onlyAttributeKeys = ['description', 'name', 'note', 'start_date'];

[Avan2021]

Hi @k-yle , please review the PR #10706 for this issue and let me know if you want me to make any changes