add markdown codeblock renderer extension point (#1492)

Introduces a new extension point that allows developers to overwrite the default syntax highlighting renderer for specific code blocks defined in markdown. The extension point is dynamic and follows the pattern "markdown-renderer.code.{language}".
This feature lays the groundwork for the scm-markdown-plantuml-plugin.

scm-ui/ui-components/src/MarkdownView.tsx

@@ -27,12 +27,12 @@ import { RouteComponentProps, withRouter } from "react-router-dom";
 import Markdown from "react-markdown/with-html";
 import { binder } from "@scm-manager/ui-extensions";
 import ErrorBoundary from "./ErrorBoundary";
-import SyntaxHighlighter from "./SyntaxHighlighter";
 import MarkdownHeadingRenderer from "./MarkdownHeadingRenderer";
 import { create } from "./MarkdownLinkRenderer";
 import { useTranslation, WithTranslation, withTranslation } from "react-i18next";
 import Notification from "./Notification";
 import { createTransformer } from "./remarkChangesetShortLinkParser";
+import MarkdownCodeRenderer from "./MarkdownCodeRenderer";
 
 type Props = RouteComponentProps &
   WithTranslation & {
@@ -81,13 +81,13 @@ const MarkdownErrorNotification: FC = () => {
 class MarkdownView extends React.Component<Props, State> {
   static defaultProps: Partial<Props> = {
     enableAnchorHeadings: false,
-    skipHtml: false
+    skipHtml: false,
   };
 
   constructor(props: Props) {
     super(props);
     this.state = {
-      contentRef: null
+      contentRef: null,
     };
   }
 
@@ -137,12 +137,12 @@ class MarkdownView extends React.Component<Props, State> {
     }
 
     if (!rendererList.code) {
-      rendererList.code = SyntaxHighlighter;
+      rendererList.code = MarkdownCodeRenderer;
     }
 
     return (
       <ErrorBoundary fallback={MarkdownErrorNotification}>
-        <div ref={el => this.setState({ contentRef: el })}>
+        <div ref={(el) => this.setState({ contentRef: el })}>
           <Markdown
             className="content is-word-break"
             skipHtml={skipHtml}