Add SAMLAG group image

[olillin]

This PR adds a group image for SAMLAG (skolavslutningsmusikledararbetsgruppen)
and the CSS to display the image without the group name.

[olillin]

Not sure why the backend fails to build since I have not changed anything there. I tried building the Docker image locally with no issues

[simon-wg]

Because rust updated their compiler it seems. I might look into it if I have time.

Error:   --> /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/metrics-0.23.0/src/recorder/mod.rs:77:9
   |
71 |       fn new(recorder: &dyn Recorder) -> Self {
   |              --------  - let's call the lifetime of this reference `'1`
   |              |
   |              `recorder` is a reference that is only valid in the associated function body
...
77 | /         LOCAL_RECORDER.with(|local_recorder| {
78 | |             local_recorder.set(Some(recorder_ptr));
79 | |         });
   | |          ^
   | |          |
   | |__________`recorder` escapes the associated function body here
   |            argument requires that `'1` must outlive `'static`
   |
note: raw pointer casts of trait objects cannot extend lifetimes
  --> /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/metrics-0.23.0/src/recorder/mod.rs:75:60
   |
75 |         let recorder_ptr = unsafe { NonNull::new_unchecked(recorder as *const _ as *mut _) };
   |                                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: this was previously accepted by the compiler but was changed recently
   = help: see <https://github.com/rust-lang/rust/issues/141402> for more information