Add example usage of podspec declarations

[piotr-cz]

Platforms affected

none

Motivation and Context

Complementing docblock for getPodSpecs function

Description

When trying to find more information about new <podspec> tag deprecating <framework type="podspec" /> I found example usage in docblock above getPodSpecs function
However it doesn't specify how to use declarations so I've copied example from specs fixture

Update: Example usage is also described in the docs.

Testing

Change in docblock, no testing required

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[codecov-io]

Codecov Report

Merging #67 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #67   +/-   ##
=======================================
  Coverage   88.87%   88.87%           
=======================================
  Files          20       20           
  Lines        1807     1807           
  Branches      370      370           
=======================================
  Hits         1606     1606           
  Misses        201      201

Impacted Files	Coverage Δ
src/PluginInfo/PluginInfo.js	83.41% <ø> (ø)	⬆️

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