Remove CI compiler version for Linux build

- Just take the default one offered in the image
- It removes the burden of iterating the version each time

Refined New Grid and Add Image icons (#642)

Change keybinding from F7 to Alt+0 in French tutorial

Make it clearer which wxWidgets to get and how

Use icons from Visual Studio Code in the toolbar (#641)

* Use icons from Visual Studio Code in the toolbar

* Fix preposition

Use vector data directly (#640)

Also calculate hash while image resampling (#639)

Set C++20 as standard in CMake project

Adjust to C++20 (#636)

* Update GitHub Actions Linux compilers

* Update MSVC project to use C++20

* Update XCode project to use C++20

* Satisfy new C++20 requirement of total equality

* Explicitly type as wxString

Otherwise MSVC gets confused.

Update version of checkout action (#632)

Old versions are deprecated, see <https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/>