[Feature request] Add save-all command

In addition to the suggested save prompt #477 on window close, i would also suggest to add these extension regarding unsaved changes:

• Provide a Save all command, like VSCode does. Preferably as keyboard shortcut (maybe Ctrl+Shift+S) and via menu.
• Add a small indicator in the tree for all requests with unsaved changes.

Currently it is hard to not loose changes of requests when closing Bruno. I have to manually go through all requests to see if there are unsaved changes.

JIRA