Feature: Iterate paragraphs and tables in document-order

In order to access paragraphs and tables in the same order they appear in the document

As a developer using python-docx

I need the ability to iterate the inner-content of a block-item-container

Scenario: Document.iter_inner_content()

Given a Document object with paragraphs and tables

Then document.iter_inner_content() produces the block-items in document order

Scenario: Header.iter_inner_content()

Given a Header object with paragraphs and tables

Then header.iter_inner_content() produces the block-items in document order

Scenario: Footer.iter_inner_content()

Given a Footer object with paragraphs and tables

Then footer.iter_inner_content() produces the block-items in document order

Scenario: _Cell.iter_inner_content()

Given a _Cell object with paragraphs and tables

Then cell.iter_inner_content() produces the block-items in document order