Update docker icons

[jpaju]

Follow up for #906. Icons for Dockerfile and a.Dockerfile don't show up correctly

[jpaju]

I'm unable to build broot locally so investigating the issue with docker icons is impossible right now. I'm on apple silicon mac and when running cargo build or cargo install I get an error:

error: linking with `cc` failed: exit status: 1
  |
  = note: env [...]
  = note: ld: library not found for -liconv
          clang-16: error: linker command failed with exit code 1 (use -v to see invocation)

error: could not compile `libz-sys` (build script) due to 1 previous error
warning: build failed, waiting for other jobs to finish...

Instructions for building broot from source only list required dependencies from Linux distros so it could be that I'm missing some dependency 🤷 @FrancescElies any ideas how to resolve this?

[FrancescElies]

@jpaju I am not aware of having installed that lib explicitely on mac, does running xcode-select --install which installs apples commandlinetools help?. Otherwise maybe try to install it with brew install libiconv

[jpaju]

I'm using nix dev shell and issue was configuring that for mac.

If someone is interested, this flake.nix did it for me

```nix { inputs.nixpkgs.url = "github:nixos/nixpkgs"; inputs.flake-utils.url = "github:numtide/flake-utils"; outputs = { nixpkgs, flake-utils, ... }: flake-utils.lib.eachDefaultSystem (system: let pkgs = import nixpkgs { inherit system; }; darwinDeps = if pkgs.stdenv.isDarwin then with pkgs; [ libiconv darwin.apple_sdk.frameworks.Security ] else [ ]; in { devShells.default = pkgs.mkShell { name = "broot"; buildInputs = with pkgs; [ rustc rust-analyzer cargo openssl pkg-config ] ++ darwinDeps; }; }); } ```

Now that I'm able to build locally, I was able to debug that the issue is in font.rs get_icon function. Before passing name, double_ext and ext to handle_file function, they are lower cased by calling .to_ascii_lowercase(). Because Dockerfile is capitalized, it fails to find icon.

I'm wondering whether it would be okay to remove .to_ascii_lowercase() from all three parameters when calling handle_file function? Quickly testing this out, it seems to be okay though 🤔