Improve question creation errors handling

[hlbmtc]

Current behavior

Currently, frontend does not notify use about any BE errors happening during question/post creations.

Expected/desired behavior

• Add errors handling for unexpected events (e.g critical BE exception)
• Add buttons loading states (disabled)
• Add console.error logging

[SylvainChevalier]

Doesn't seem blocking for launch, am I missing something?