Remove official support for QMake (#3839)

* delet chatterino.pro

* Update documentation

* Update Github Actions config

* Update Cirrus CI config

* Attempt to fix Cirrus CI

* Add changelog entry

* Delete tools/update_filelist.py

It was a QMake-only script? Maybe will need revert + change to CMake or something?

* fix?

* Fuck this linter

* Attempt to clean up build.yml a little

* Add cmaake to install list, remove step for qmake PATH

* Change list entries to always use 1.

Sneaky unrelated change

* These are no longer tests!

* FUCK YOU PRETTIER

* Make BUILDING_ON_LINUX.md simpler

* Get rid of Jenkins

* Get rid of travis

* Remove dupes

* Remove appveyor

* Remove qmake from conanfile

* Try removing explicit qmake path

* Nothing uses the qt style plugins installer anymore

* Update manual linux building instructions

* Update freebsd compilation instructions with a copy paste from the linux instructions

* Remove unused docker files

* Remove linux breakpad build script as it's unused

* Update changelog entry phrasing

* Lint build markdown files

* Change top changelog entry to not be confused as a link

* Skip QtCreator conan setup if conan is disabled

This reduces the amount of warnings & errors Windows users get with
QtCreator

* lint building on linux file

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

CMakeLists.txt

@@ -30,6 +30,8 @@ endif()
 if (USE_CONAN OR CONAN_EXPORTED)
     include(${CMAKE_CURRENT_BINARY_DIR}/conanbuildinfo.cmake)
     conan_basic_setup(TARGETS NO_OUTPUT_DIRS)
+else ()
+    set(QT_CREATOR_SKIP_CONAN_SETUP ON)
 endif()
 
 find_program(CCACHE_PROGRAM ccache)