[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>

applications/examples/example_apps_assets/README.md

@@ -1,7 +1,11 @@
-# Apps Assets folder Example
+# Apps Assets folder Example {#example_app_assets}
 
 This example shows how to use the Apps Assets folder to store data that is not part of the application itself, but is required for its operation, and that data is provided with the application.
 
+## Source code
+
+Source code for this example can be found [here](https://github.com/flipperdevices/flipperzero-firmware/tree/dev/applications/examples/example_apps_assets).
+
 ## What is the Apps Assets Folder?
 
 The **Apps Assets** folder is a folder where external applications unpack their assets.