Add user feedback when they have reached character limit on text inputs

[pmarsh-scottlogic]

Since PR #503 we have a maximum number of characters allowed in our defence config text inputs. We will soon be limiting the chatbox input as well (#507). When the user hits that character limit, we simply stop them from being able to add more text. There is no indication why they can't add more characters, or that it's intentional. Maybe they'll think that their keyboard is faulty!

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For this ticket we want to let the user know that they have hit the character limit. We will want some UX input on this, for there are several options including:

• Some sort of error popup/tooltip
• Error text that sits below the input box, similar to the success text. example below

[chriswilty]

Recommend doing #93 before this issue.