fix side by side margins and highlight usage of object instead of map

Author: rtfpessoa

src/ui/css/diff2html.css

@@ -113,8 +113,6 @@
   overflow-x: scroll;
   overflow-y: hidden;
   width: 50%;
-  margin-right: -4px;
-  margin-bottom: -8px;
 }
 
 .d2h-code-line {

src/ui/js/diff2html-ui-base.ts

@@ -146,6 +146,10 @@ export class Diff2HtmlUI {
 
       const language = file.getAttribute('data-lang');
 
+      if (!(this.config.highlightLanguages instanceof Map)) {
+        this.config.highlightLanguages = new Map(Object.entries(this.config.highlightLanguages));
+      }
+
       const hljsLanguage =
         language && this.config.highlightLanguages.has(language)
           ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion