Set hierarchical header levels (#1101)

[bruceplai]

Closes #1101

• Set aria-level values in multiple pages

• Some code formatting

[codeclimate[bot]]

Code Climate has analyzed commit 99f7b2c9 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 80.7% (0.0% change).

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