Adding observable rendering

[shancarter]

Adding a function for rendering cells from observable notebooks in python notebooks.

Example usage:

renderObservable(
    "@shancarter/untitled/2", 
    cells=[ "viewof width", "viewof stage"], 
    data={"height": 400}
)

[coveralls]

Pull Request Test Coverage Report for Build 463

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.05%) to 81.923%

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Totals
Change from base Build 459:	-0.05%
Covered Lines:	1491
Relevant Lines:	1820

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💛 - Coveralls