Suggest Tweets for @pharoproject

It is not that easy to stay on top of tweeting (or even retweeting) with https://twitter.com/pharoproject 

To make it easier, we have added a form:

- the form then is checked manually every couple of days and the useful submissions will be turned into tweets

   (the process for now is very manual but might be improved)

- I added the Form link to the Twitter bio and https://www.pharo.org/community

Marcus