Add Steam, Discord, and Youtube to profile

[HebaruSan]

Motivation

While deleting spammers, I noticed that the non-spammers in the user list frequently pasted three socials into their descriptions or other fields:

• Steam user
• Discord user
• Youtube user

These services are commonly used in the KSP and KSP2 communities and it is convenient for users to be able to identify one another this way.

Changes

Now these fields are added to the user profile.

• [x] Just realized I forgot to add them to the admin pages user list's "Socials" column