Expand documentation of ZitiQL filtering language

[sabedevops]

The filter language description given below is incomplete:

https://openziti.github.io/api/rest/shared-api-capabilities/

For example, it lacks a descrition of the following valid filter:

GET /edge/client/v1/services?filter=anyOf(configs) contains ":configId"

The full grammar is described here for reference: https://github.com/openziti/storage/blob/main/zitiql/ZitiQl.g4

[qrkourier]

More examples would be helpful beyond merely linking to the grammar def as we do currently, if only because it's not obvious to me from looking at the grammar def how to compose a valid filter like anyOf() or allOf().

[sabedevops]

Some additional resources: https://github.com/openziti/storage/blob/74087e8052b7cb0fb69854e50570d3e8c7bca8c2/ast/README.md https://github.com/openziti/storage/blob/74087e8052b7cb0fb69854e50570d3e8c7bca8c2/ast/node.go#L108

Also useful are the test files: https://github.com/openziti/storage/blob/74087e8052b7cb0fb69854e50570d3e8c7bca8c2/ast/bolt_listener_test.go