manager: some parts of documentation for version 6

Unfinished parts from this MR are tracked in #796.

---

Goal of this MR is to have a almost finished documentation for version 6. Parts that will not be finished should have a linked issue created by the time this is merged.

GitLab pages with documentation (probably, but not necessarily from this branch)

Step 1

• getting started section
• rewrite pages about Lua configuration with declarative configuration
  • syntax and conventions (this might be already rewritten somewhere)
  • modules
  • networking
  • performance and resiliency
  • policy, access control and data manipulation
  • logging, monitoring, diagnostics
  • DNSSEC, data verification
  • experimental features
• for developers section
  • internal architecture
• deployment guide
  • manual
  • systemd
  • docker
  • multiple instances
• extending the resolver
• create gitlab issues for all documentation sections that won't be fully completed with this MR

Step 2

1. run spell checker
2. collect feedback from @vcunat
3. implement feedback
4. collect feedback from @llhotka
5. implement feedback
6. collect feedback from someone unrelated to the dev team (ODVR admins, someone random, ...)
7. implement feedback

doc/README.md

@@ -5,28 +5,35 @@ It does not however contain API documentation, which is built separately in this
 
 ### Requirements
 
+To generate documentation you need to install [meson][meson] and [ninja][ninja].
+
 The code is documented with [Doxygen][doxygen] JavaDoc style, a prettified documentation
-also requires [breathe][breathe], [Sphinx][sphinx] and [Sphinx tabs][sphinx-tabs] for building sane documentation pages.
-It is not however required.
+also requires [breathe][breathe], [Sphinx][sphinx], [Sphinx tabs][sphinx-tabs] and [Sphinx Read the Docs theme][sphinx_rtd_theme] for building sane documentation pages.
 
+[meson]: https://mesonbuild.com/
+[ninja]: https://ninja-build.org/
 [doxygen]:https://www.stack.nl/~dimitri/doxygen/manual/index.html
 [breathe]: https://github.com/michaeljones/breathe
 [sphinx]: http://sphinx-doc.org/
 [sphinx-tabs]: https://sphinx-tabs.readthedocs.io/
+[sphinx_rtd_theme]: https://sphinx-rtd-theme.readthedocs.io/en/stable/
 
-You can get the extra dependencies with pip:
+You can install dependencies with pip:
 
 ```sh
-pip install -U Sphinx sphinx-tabs breathe
+pip install -U Sphinx sphinx-tabs sphinx_rtd_theme breathe
 # Alternatively
-pip -r doc/requirements.txt
+pip install -r doc/requirements.txt
 ```
 
 ### Building documentation
 
-If you satisfy the requirements, it's as easy as `make doc`, which builds the documentation in this folder `doc/html`.
+If you satisfy the requirements, the documentation will be generated to `doc/html` directory.
+You must be in the root directory of the project.
+
+It may be needed to initialize git submodules `git submodule update --init --recursive`.
 
 ```sh
-$ meson build_dir -Ddoc=enabled
+$ meson setup build_dir -Ddoc=enabled
 $ ninja -C build_dir doc
 ```