Add note about SPEED in output
Add note about SPEED in output

In #8823 it was pointed out that the `SPEED` value wasn't documented
anywhere.

explosion/spaCy,explosion/spaCy,explosion/spaCy,explosion/spaCy,explosion/spaCy,explosion/spaCy,honnibal/spaCy,honnibal/spaCy,honnibal/spaCy,honnibal/spaCy