[ENHANCEMENT] Display possible arguments when using a WHILE loop

[johndoorzon]

Is your enhancement request related to a problem? Please describe.
When I use a WHILE loop, I frequently use one or more of the possible arguments: limit, on_limit and on_limit_message to improve error handling
RobotCode does not give me hints that there are arguments I can use in combination with the WHILE, so I have to google them to know which ones there are.

Describe the solution you'd like
When I use a WHILE loop, I would like RobotCode to give me hints to possible arguments, for example when I place a tab after
"WHILE ${condition}"
(like when you fill arguments with a keyword)

[d-biehl]

good idea!!!