starship: expose presets in share/starship/presets

expose starship presets so they can be imported into user configuration,
e.g. `with builtins; (fromTOML (readFile "${starship}/share/starship/presets/SOMEPRESET.toml"))`

this allows merging of presets and could be further used by e.g. Home
Manager modules

pkgs/tools/misc/starship/default.nix

@@ -33,6 +33,10 @@ rustPlatform.buildRustPackage rec {
       --bash <($out/bin/starship completions bash) \
       --fish <($out/bin/starship completions fish) \
       --zsh <($out/bin/starship completions zsh)
+
+    presetdir=$out/share/starship/presets/
+    mkdir -p $presetdir
+    cp docs/.vuepress/public/presets/toml/*.toml $presetdir
   '';
 
   cargoHash = "sha256-ZHHrpepKZnSGufyEAjNDozaIKAt2GFRt+hU2ej7LceA=";