Interface: "waiting..." icon while processing

Created by: famuvie

Include some symbol to ask for patience while calculations take place

See, for instance, https://github.com/epi-interactive/loading, which includes a minimalistic progress bar and a "skeleton" of the resulting contents in the meanwhile.

removed time estimate

changed milestone to %mapMCDA hackathon

added good first issue label

created branch 33-interface-waiting-icon-while-processing to address this issue

mentioned in merge request !5 (merged)

See https://stackoverflow.com/a/49488972

assigned to @oumaima.mtaallah

mentioned in commit bf4c6f63

closed with merge request !5 (merged)