rsdlEditor: update grammar to match current ABNF

[ralfhandl]

rsdlEditor uses a lezer-rsdl.grammar for RSDL which is out of sync with the current ABNF

• enum types can only be defined within a service (where they can't) instead of next to a service and other types
• key as a property name isn't treated correctly (RSDL Editor doesn't distinguish property named "key" from keyword #367)

See https://lezer.codemirror.net/docs/guide/#overview for lezer grammar syntax