Crate-docs-theme

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- Deleted unused modules
- Fixed template logic

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- Moved Admin UI and Crash into the CrateDB section.

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- Updates for docs reshuffle, including nav bar update and module name changes.

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- Edited a function that shows/hides the toggled docs menu on mobile.
- Changed ``z-index`` of ``header.header-nav`` so ``version-select-container``
won't overlap on mobile
- Changed ``Edit on GitHub`` link from ``blob`` to ``edit`` in ``layout.html``

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- Removed a function that hides the toggled docs menu on mobile.

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- Changed ``width`` to ``100%`` and ``max-width`` to ``400px`` on
``.main-nav`` for tablet and mobile to prevent overflow on smaller
devices in ``custom.css``.
- Added ``minWidth: 992`` for ``sticky-sidebar`` to ``layout.html`` to
fix scroll issues on mobile devices.
- Removed ``60px`` padding in ``.toctree`` to get rid of the whitespace.
- Added ``20px`` margin below to ``.bs-docs-sidebar`` so the ``h1`` won't
overlap.