Better Onboarding: New Welcome DM & Intro Channel

Hi! I have just done 2 changes to hopefully make new user experience better.

I suspect that new members may feel not welcome enough and with the recent removal of welcome channel they don't have much to go about, apart from the welcome DM from the @Make Money Online bot and some may miss it or just throw it off as a automated message. I have removed that channel, because as suspected scammers used it to target new joiners and I value safety of my members the most, so I think that that's an appropriate change.

Here's the new changes:
- I have rewritten the welcome DM to make it more appealing by shortening it and adding emojis to interest people into reading. I show a screenshot below for comparison.
- I have also added a brand new channel #👋・introductions, you can choose to introduce yourself in it by following our pinned scheme or writing something from yourself. You can expect a welcome from me or other active members. If you choose to welcome people, please do so in their threads or by reacting, and thank you!
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