[FL-870] Auto-generated firmware documentation take two (#2944)

* Add doxygen and doxygen-awesome css, cleanup docs files
* Ignore more libraries and remove leftover local variables
* Create an actual intro page
* .md files linting
* Add doxygen action
* Fix Doxygen path
* Fix doxyfile path
* Try to upload
* Change docs branch
* Add submudules checkout
* Disable doxygen on PR
* Mention the firmware docs in the readme
* More dev docs mentions in the readme
* Fix runner group, add tags
* Test dev in PR
* Disable running on PR
* Fix a typo in the doxyfile
* Try upload to S3
* Fix local path
* Fix S3 ACL
* Add delete flag, unifying dev and tags
* Update ignored directories
* More ignored directories
* Even more ignored directories
* Fix submodule
* Change S3 uploader
* Change S3 uploader version
* Fix aws sync flags
* Fix ACL
* Disable ACL
* Improve ignores, add WiFi devboard docs
* TEMP: generate dev docs
* TEMP: generate 0.89.0 docs
* Disabling PR trigger
* Enable submodules and test build
* Enable test build
* Disable test build
* Change docs directory structure
* Fix accidentally committed submodule
* Fix submodules
* Update links to the developer documentation
* Markdown linting
* Update workflow, enable test build
* Fix doxygen dir path
* Update Doxyfile-awesome.cfg
* Change paths
* Fix upload docs path
* Disable pull_request debug trigger
* Disable tags building
* Remove autolinks and namespaces
* Establish basic documentation structure
* Add missing changes
* Improve stylesheet, move some files
* Improve examples
* Improve the main page
* Improve application dev docs
* Improve system programming docs
* Improve development tools docs
* Improve other docs
* Improve application examples
* Fix formatting
* Fix PVS-studio warnings
* Improve visuals
* Fix doxygen syntax warnings
* Fix broken links
* Update doxygen action

Co-authored-by: DrunkBatya <drunkbatya.js@gmail.com>
Co-authored-by: あく <alleteam@gmail.com>
Co-authored-by: Georgii Surkov <georgii.surkov@outlook.com>
Co-authored-by: Georgii Surkov <37121527+gsurkov@users.noreply.github.com>

documentation/doxygen/index.dox

@@ -0,0 +1,25 @@
+/**
+@mainpage Overview
+
+Welcome to the Flipper Zero Firmware Developer Documentation!
+
+This documentation is intended for developers who want to modify the firmware of the Flipper Zero.
+
+If you are looking for the user manual, please visit the [User Documentation](https://docs.flipperzero.one/) instead.
+
+The documentation is divided into several sections, with all of them accessible from the sidebar on the left:
+
+- @ref applications - Writing applications for Flipper Zero
+- @ref system - Understanding the firmware's internals
+- @ref file_formats - Saving and loading data to and from files
+- @ref dev_tools - Hardware and software tools for all kinds of programming
+- @ref expansion - Additional modules to expand Flipper's consciousness
+- @ref misc - Various useful pieces of information
+
+Aside from the manually-written documentation files, there's also a few automatically-generated ones at the bottom of the sidebar:
+
+- [Data Structures](annotated.html) - Every data structure in a list
+- [Files](files.html) - Source file tree with easy navigation
+
+These are generated from the source code and are useful for quickly finding the source code or API documentation for a particular function or data structure.
+*/