Add limits info

[TrevorSayre]

Embeds have some limits:

• Title is limited to 256 characters
• Description is limited to 4096 characters
• An embed can contain a maximum of 25 fields
• A field name/title is limited to 256 character and the value of the field is limited to 1024 characters
• Footer is limited to 2048 characters
• Author name is limited to 256 characters
• The total of characters allowed in an embed is 6000

It would be helpful to add some (maybe toggle show/hide) character counters and field counters. While text already stops when you hit the character count limit, and you already get an error message when trying to add a 26th field, etc. knowing how close you are to hitting the cap can be helpful. The overall 6000 character limit is especially tough to add up as you're developing an embed.