improving the advanced indexing notebooks (#264)

* adding the links to all indexing materials

* typo fix + remove a redundant example.

* updates to indexing

* updating advanced indexing

* advanced indexing

* update indexing redundancies

* adding excercise

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* few fixes for build fail

* updating header

* updating header

* align with new exercise syntax

* adding advanced indexing

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* add numpy advanced indexing

* update learning objectives

* few minor updates and wording changes

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* update indexing docs

* quick merge conflict resolve

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* update docs

* adding np.ix_

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* fix merge

* typo fix

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Scott Henderson <[email protected]>
Co-authored-by: Scott Henderson <[email protected]>