DOC: Transfer the wiki FAQ page to Markdown documentation

Transfer the wiki FAQ page to Markdown documentation:
https://itk.org/Wiki/ITK/FAQ

Add the corresponding entry in the `Learn` section of the documentation
index, and set the `maxdepth` to 1 to avoid showing the FAQ page
sections.

Take advantage of the transition to:
- Update URLs, including changing `http` to `https`, fixing broken URLs,
  etc.
- Link ITK and VTK classes to their Doxygen documentation pages.
- Highlight parts (e.g. class names) using Markdown syntax.
- Refactor the data format section to: include mesh and point set, and
  transform file format sections, mention other file formats potentially
  supported by remote modules. Add links to the file format reference
  pages, and the Doxygen documentation of the ITK IO classes involved.
- Make the BibTeX list style consistent, remove broken URLs pointing to
  old versions of the SW Guide or all pointing to the latest PDF
  available online, etc.
- Remove outdated paragraph about libraries to build visualization
  applications.
- Change mentions to `ImageViewer` to `itkwidgets`.
- Prefer pointing to the Python `imageio` package over `ImageMagick`.
- Mention `itk-wasm dicom` to read a volume from a DICOM series.
- Reword the language binding section: remove Java and mention that
  further bindings are available through SimpleITK and itk-wasm.
- Remove the `What does \`Error opening hint file NOTFOUND\` mean?`
  section.
- Remove the language binding/wrapping section, as it is outdated: it
  refers to the current SWIG wrapping before it was integrated into the
  ITK repository.
- Remove mentions to section number and pages in the ITK SW Guide, as
  they have changed and may change in the future.
- Remove the emacs coding style section, and the outdated paragraph
  about the CMake indentantion and syntax Vim file.
- Rewrite the Vim coding style section, as ITK's coding style is now
  enforced and/or checked automatically, and as ITK switched from
  `txx` to `hxx` suffices some time ago.
- Remove the empty `What is the `\`ITK_TEMPLATE_VISIBILITY_DEFAULT\`
  CMake option?` section.
- Remove the outdated `Platform-specific questions`section.
- Fix typos and grammar, and reword passages for better understanding.
- Change the title to `Frequently asked questions`.

Documentation/docs/index.md

@@ -26,12 +26,13 @@ licenses
 
 
 ```{toctree}
-:maxdepth: 3
+:maxdepth: 1
 :caption: 📖 Learn
 
 Examples <https://examples.itk.org>
 Tutorial <https://github.com/InsightSoftwareConsortium/ScientificImageAnalysisVisualizationAndArtificialIntelligenceCourse>
 Software Guide <https://itk.org/ItkSoftwareGuide.pdf>
+learn/faq.md
 learn/courses.md
 ```