vivid: replace theme content from yaml with json

This should fix missinterpretation of hex colors (which should be a
string) as numbers in scientific notation. For example: 1e2030.

modules/programs/vivid.nix

@@ -138,7 +138,7 @@ in
       // (lib.mapAttrs' (
         name: value:
         lib.nameValuePair "vivid/themes/${name}.yml" {
-          source = if lib.isAttrs value then yamlFormat.generate "${name}.yml" value else value;
+          source = if lib.isAttrs value then pkgs.writeText "${name}.json" (builtins.toJSON value) else value;
         }
       ) cfg.themes);
 

tests/modules/programs/vivid/themes/tiny.yml

@@ -1,9 +1 @@
-colors:
-  primary: 00aaff
-  secondary: ff00aa
-core:
-  directory:
-    foreground: primary
-  executable-file:
-    font-style: bold
-    foreground: secondary
+{"colors":{"primary":"00aaff","secondary":"ff00aa"},"core":{"directory":{"foreground":"primary"},"executable-file":{"font-style":"bold","foreground":"secondary"}}}