[Docs] Pulling a nested bundle should allow filtering

# Use Case
As an Application consumer
When filtering nested bundles
I want to read friendly, easy to learn documentation
So that I learn about the capabilities of the pull command
And so that I can easily use / debug / fix any issues using the tool

# Description

📚 Documentation: Navigation
Given I want to learn how to filter a nested bundle
When I navigate through imgpkg documentation
Then I intuitively find the reference that describes the pull command and the --recursive-filter flag

🔍 Documentation: Search
Given I want to learn how to filter a nested bundle
When I search for the most obvious search terms: "recursive", "nested bundles", "filter"
Then I see results that when I click on them take me to the most relevant reference for this flag.

Start by locating the imgpkg pull-command reference and the --recursive-filter documentation, then check how documentation navigation and search terms are defined. Done means users can find the nested-bundle filtering reference through navigation and searches for “recursive,” “nested bundles,” and “filter,” with the flag’s behavior explained clearly.

Written by the indexing model from the issue text.