Use clang-format with Qt style

[alexfikl]

The Qt style was copied from https://code.qt.io/cgit/qt/qt5.git/tree/_clang-format
There's also a KDE style at https://invent.kde.org/frameworks/extra-cmake-modules/-/blob/master/kde-modules/clang-format.cmake

Applied using

fd -e h -x clang-format -i
fd -e cpp -x clang-format -i

[alexfikl]

I'm not a big Qt/C++ programmer these days, so I don't have a preference besides just having some consistent formatting. We can use another .clang-format config if that fits better with the project.

[alexfikl]

@jfmcarreira (soft ping) Have you had a chance to look at this?

[jfmcarreira]

I was not fully aware the lack of formatting rules in this repository. We can go with this one. And thanks for the ping, as I had forgot it

[alexfikl]

I was not fully aware the lack of formatting rules in this repository. We can go with this one. And thanks for the ping, as I had forgot it

No worries and thank you for merging this! 🎉

For what it's worth, the codebase seemed pretty consistent, but I'm not sure what style it was using. This looks like a lot of changes because it used tabs instead of spaces for indentation.. so pretty much every line was changed :\