fix: allow 'include' directive in 'if' and 'limit_except' blocks

[dareste]

Proposed changes

Resolves #72.

The mask ngxAnyConf is defined as "any context except server > if, location > if and location > limit_except".

Given that this mask is only used for defining the valid contexts for the include directive, and given that the contexts listed above are valid for include, it makes sense to modify the ngxAnyConf definition to include such contexts.

Checklist

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• [x] I have read the CONTRIBUTING document
• [x] If applicable, I have added tests that prove my fix is effective or that my feature works
• [x] If applicable, I have checked that any relevant tests pass after adding my changes
• [x] I have updated any relevant documentation (README.md)

[ornj]

I don't know why the original definition of this mask omitted if contexts and limit_except. This went all the way back to the original Python without a useful commit message or hint as to why it was implemented this way.