feat(fish): convert a few functions

fish/functions/dataUrl.fish

@@ -0,0 +1,7 @@
+function dataUrl --description "Create a data URL from a file"
+    set mimeType (file -b --mime-type $argv)
+    if string match -r '^text/' $mimeType
+        set mimeType "$mimeType;charset=utf-8"
+    end
+    echo "data:$mimeType;base64,(openssl base64 -in $argv | tr -d '\n')"
+end