调整字符宽度

逗号加宽，f右间距加宽

Author: Linho1219

public/fonts/KaTeX_AllInOne.woff2

@@ -1,7 +1,7 @@
 <template>
   <div class="input-inner">
     <div class="field main-fn">
-      <FunctionField class="fn" label="f(x, y)" v-model="self.fn" />
+      <FunctionField class="fn" label="f(x,y)" v-model="self.fn" />
       <span class="label styled"> =0 </span>
     </div>
     <AnimatedFold :folded="props.folded">