docs: Reorganize pages, update homepage content, and implement tiles on the homepage

[dgmccart]

To improve navigation of the site, we plan 3 updates detailed below. These updates are motivated by the diataxis framework for documentation.

• [x] Update the content on the homepage
• [x] Reorganize the pages on the site to simplify the top level navigation and add educational articles
• [ ] Implement tiles on the homepage to improve the UX, especially for first time visitors. (See screenshot below of mockup from the Acquire site. Unlike the Acquire docs theme, our theme provides this design element.)

[dgmccart]

Tasks for updating content on the homepage:

• [x] Delete the CryoET Workflow Overview section
• [ ] Replace content in Getting Started with the tiles detailed in a comment below.
• [x] Add to the bottom of the Amazon Web Services S3 Bucket Info section: "Refer to [this how-to guide](link to the Download Data page) for information on downloading data from our AWS S3 bucket."

[dgmccart]

Tasks for reorganizing the pages on the site to simplify the top level navigation and add educational articles:

• [x] Update top level nav to: Home, Quick Start, Python API, Tutorials, About CryoET, FAQ (Note: About CryoET is a new section that will need its own landing page)
• [x] Home links to the documentation home page
• [x] Quick Start links to the quick start guide
• [x] Python API links to the API reference
• [x] Tutorials links to the tutorials landing page with 4 tiles (see comment below)
• [x] About CryoET links to a new landing page with 2 tiles (see comment below)
• [x] FAQ links to the existing FAQ

[dgmccart]

On the tutorials landing page, replace the bullets with 4 tiles (title - description is the format used below):

• [x] Top left: Download Data - Guide on downloading data from the AWS S3 bucket (link to Download data page)
• [x] Top right: Examples - Short code snippets using the API (link to the examples page)
• [x] Bottom Left: napari Plugin - Quick start guide on using napari for visualizing data (link to the Using napari page)
• [x] Bottom right: Predicting Sample Boundaries - End to end tutorial from downloading data to analyzing tomograms (link to this tutorial)

[dgmccart]

Create About CryoET landing page with tiles (title - description is the format used below):

• [ ] Intro paragraph: Learn about CryoET data and how to navigate the CryoET Data Portal (I had a typo in the original copy, which I have fixed now.)
• [x] Left tile: Intro to CryoET - Learn about the capabilities and acquisition of CryoET data (link to the new Intro to CryoET article)
• [ ] Right tile: Data Organization - Guide on how the CryoET Data Portal is organized (link to the existing data organization page)

[dgmccart]

Once these updates are complete, links on the pages of the docs site and on the Portal UI site will need to be adjusted to point to the new locations. Updates to the Portal UI links are tracked in this issue #1111

[dgmccart]

Whoops! I forgot to add a description of what the tiles for the homepage should have.

On the homepage, replace the bullets with 4 bullets in the Getting Started section with 4 tiles (title - description is the format used below):

• [ ] Top left: Get Started - Install and start using the Python Client API (link to Quick Start Guide)
• [ ] Top right: API Reference - Information on the Python Client API Classes (link to anchor on the API reference: https://chanzuckerberg.github.io/cryoet-data-portal/python-api.html#module-cryoet_data_portal)
• [ ] Bottom Left: Tutorials - Examples of selecting, downloading, and visualizing data from the Portal (link to the Tutorials landing page)
• [ ] Bottom right: About CryoET - Learn about CryoET data and how to use navigate the CryoET Data Portal (link to the About CryoET landing page)