Improve form validation ont the Record Call page

[brenocastelo]

When trying to submit a Call, I noticed some points on the form validation that might be improved for a good UX.

• Input character limits:
  I fought a little to describe my title, since the characters limit is 50. I needed to reduce/change the words a couple of times before summiting it. I felt that if I had a bit more space, my title could have been a little more descriptive.
  I think it would be nice to have a “character countdown” to show us if we are close to the limit and stop to allow us to type after achieving it.

• The validation only happens after clicking on the submit button. It would be nice if it happened as soon as it found something invalid.

• There are some differences between the validation messages. For the limit validation, it's displayed a red text. For the empty field validation, it's displayed the default HTML validation and another point is that the empty validation takes priority over the limit validation. In the second image, the title input has more than 50 characters, but only the feedback to the empty validation is displayed.

See images below