Previously, the only way to select all the module labels was with the
following kind of selector:
```css
.modules-left > widget > label,
.modules-center > widget > label,
.modules-right > widget > label {
/* ... */
}
```
(and a matching block for the `box` containers).
Now, this can be expressed as
```css
label.module, box.module {
/* ... */
}
```
There were two main issues with fmtlib and C++20 mode:
- `fmt::format` defaults to compile-time argument checking and requires
using `fmt::runtime(format_string)` to bypass that.
- `std::format` implementation introduces conflicting declarations and
we have to specify the namespace for all `format`/`format_to` calls.
The first crash occurs when trying to parse the
ID of a workspace as an uint, since named
workspaces has negative IDs. This is fixed by
using ints for workspace IDs instead of uints.
The second crash occurs when converting a
workspace name that isn't a number to an integer.
This is fixed by wrapping std::stoi in a try
block and only sorting by number, when both names
can successfully be converted to integers.