General docs improvements for v3.0 (#2280)

* Split the docs into sections

* Split the options page into two pages - so the reference is more clean

* Reorder/Tidy up this 'deliver' page to make auto-deploy more obvious

* Fix up some links

* Merge the platform docs into a single page to clean up the navbar.

* Split the setup page to make a page dedicated to CI setup

* Move general platform-specific information into the platforms page

* Tidy up the platforms page

* Remove some redundancy in the cpp/platforms docs

* Clarify this section

* Move another FAQ entry to the platforms page

* Remove some out-of-date entries from the FAQ

* A few corrections to the options page

* Fix some broken links

* Improve the Docker references

* Update bump version filename

* Improve options TOC information density

* whitespace

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

* Convert the normal test invocation to `pytest ./tests`, not placeholder

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

mkdocs.yml

@@ -20,20 +20,18 @@ extra_javascript:
 
 nav:
   - Home: index.md
-  - User guide:
+  - Guide:
     - setup.md
-    - options.md
+    - ci-services.md
     - deliver-to-pypi.md
-    - cpp_standards.md
     - faq.md
+    - cpp_standards.md
+  - Reference:
+    - platforms.md
+    - configuration.md
+    - options.md
     - working-examples.md
-  - Supported Platforms:
-    - platforms/linux.md
-    - platforms/windows.md
-    - platforms/macos.md
-    - platforms/ios.md
-    - platforms/pyodide.md
-  - About the project:
+  - About:
     - contributing.md
     - changelog.md