Reserved key words can be used as variables

[remcowesterhoud]

Describe the bug
In our parser we keep a list of reserved key words. These key words prevent users from using variables with these names. One such an example is else.

This list does not contain all the key words we know in the FEEL engine. This means users could still use some of them as variables. The ones that are missing are:

• some
• every
• if
• for
• between
• instance
• of
• not

Environment

• FEEL engine version: Not sure. Probably all. It's definitely on the latest main branch.