Update docs for variables about website

[chipzoller]

Can you or @kacejot help me understand the action item for the docs in this issue? It seems like these linked PRs just address existing functionality and nothing new in the way of variables is introduced.

[chipzoller]

bump, @JimBugwadia and/or @kacejot. Someone please help me understand what/if are the relevant pieces of information that need to be added/changed in the docs. I'm not able to see anything user-facing that needs to be changed.

[JimBugwadia]

Hi @chipzoller - the main user facing changes are:

• $(..) is now supported for nested substitutions and generally everywhere variables are supported
• {{ @ }} can be used as the current resource path. This will be used often for custom JMESPath functions in 1.3.6. Here is an example.

We can hold this for 1.3.6.

[JimBugwadia]

Another example: https://github.com/kyverno/kyverno/blob/main/pkg/engine/variables/vars_test.go#L243

[kacejot]

We need to add syntax details described here:
https://kubernetes.slack.com/archives/CLGR9BJU9/p1619087425497900?thread_ts=1618941805.454200&cid=CLGR9BJU9