Proposals listing page is misleading if no proposals are displayed #536

If you go to the proposal page and it's empty, it may mean three cases:

1. the proposals are being loaded
2. the proposals were fetched but the chain didn't have any proposals
3. the proposals query failed

For the end user it's unclear if what of these cases have occurred unless they go to DevTools and investigate it by themselves.

I suggest updating it to do the following:

• for 1) add a spinner on the page to show it's being loaded
• for 2) display a notification with "There are no proposals" or something similar
• for 3) display a notification with "There was an error fetching proposals: " or something similar

That should improve the overall user experience of proposals listing.

(Real-life example: I was trying to see Composable proposals: https://ping.pub/composable/gov, and all of the nodes are returning 5xx on proposals query, but I had no way of knowing this just by looking at the page until I opened DevTools in my browser and saw that the queries failed)