Dalle bot improvements

[Cosmin96]

Hi! My friends and I made some improvements to the bot:

• all images are collated in a single file now so the bot only replies once
• it replies to the user with the image
• once images are generated, it deletes the in progress message
• the image also contains the title of the query (the font is open source)

[rawandahmad698]

This is nice, thank you.