Fix a bug where markdown files fail to render in the diff view. (#1202)

Motivation:

Prism raises an exception if a markdown file is specified in the commit
diff view. Because the markdown syntax is not imported from
`'prismjs/components/*`.

```js
framework-0e8d27528ba61906.js:9 Error: The language "markdown" has no grammar.
    at Object.highlight (1809-d263923ea021c688.js:8:3755)
    at [[...path]]-3633ecc2aa697c21.js:1:2753
    at Object.renderContent ([[...path]]-3633ecc2aa697c21.js:1:2844)
    ...
```

Modifications:

- Support more widely used languages by declaring
`prismjs/components/<lang>`
- Fall back to the plantext mode if `Prism` raises an exception.
- Minor) Move Java files for test servers to `webapp/javaTest` for
easier discovery.

Result:

Markdown files are now correctly rendered in the diff view.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Expanded syntax highlighting with support for JSON5, Markdown, Python,
Sass, XML, and Docker formats.

* **Bug Fixes**
  * Added a fallback to render plain text if syntax highlighting fails.

* **Chores**
  * Adjusted test source locations used by builds.
  * Added an automated task to install browser testing tooling.
* Updated style-check suppressions to include additional internal and
test-related paths.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: ikhoon

settings/checkstyle/checkstyle-suppressions.xml

@@ -5,8 +5,8 @@
 
 <suppressions>
   <!-- Suppress Javadoc-related checks in non-public code. -->
-  <suppress checks="MissingJavadocPackage|MissingJavadocType|MissingJavadocMethod" files="[\\/](examples|internal|it|jmh|test)[\\/]" />
-  <suppress checks="JavadocPackage" files="[\\/](examples|it|jmh|test)[\\/]" />
+  <suppress checks="MissingJavadocPackage|MissingJavadocType|MissingJavadocMethod" files="[\\/](examples|internal|it|jmh|test|javaTest)[\\/]" />
+  <suppress checks="JavadocPackage" files="[\\/](examples|it|jmh|test|javaTest)[\\/]" />
   <!-- Suppress all checks in generated sources. -->
   <suppress checks=".*" files="[\\/]gen-src[\\/]" />
   <!-- Suppress UncommentedMain for the server entry point -->

webapp/build.gradle

@@ -20,6 +20,17 @@ dependencies {
     testImplementation libs.shiro.core
 }
 
+sourceSets {
+    test {
+        java {
+            srcDir 'javaTest/java'
+        }
+        resources {
+            srcDir 'javaTest/resources'
+        }
+    }
+}
+
 task installPlayWright(type: NpmTask) {
     dependsOn tasks.npmInstall
     args = ['run', 'playwright:install']

webapp/src/test/java/com/linecorp/centraldogma/webapp/SamlCentralDogmaTestServer.java renamed to webapp/javaTest/java/com/linecorp/centraldogma/webapp/SamlCentralDogmaTestServer.java

@@ -8,9 +8,15 @@ import { extensionToLanguageMap } from 'dogma/common/components/editor/FileEdito
 import Prism from 'prismjs';
 // Load the language needed
 import 'prismjs/components/prism-json';
+import 'prismjs/components/prism-json5';
 import 'prismjs/components/prism-javascript';
 import 'prismjs/components/prism-yaml';
 import 'prismjs/components/prism-toml';
+import 'prismjs/components/prism-markdown';
+import 'prismjs/components/prism-python';
+import 'prismjs/components/prism-sass';
+import 'prismjs/components/prism-xml-doc';
+import 'prismjs/components/prism-docker';
 import 'prismjs/themes/prism.css';
 
 function normalize(file: FileDto[]): [string, string][] {
@@ -60,12 +66,16 @@ function highlightSyntax(path: string, str: string): React.JSX.Element {
     return <pre style={{ display: 'inline' }}>{str}</pre>;
   }
 
-  return (
-    <pre
-      style={{ display: 'inline' }}
-      dangerouslySetInnerHTML={{ __html: Prism.highlight(str, Prism.languages[language], language) }}
-    />
-  );
+  try {
+    return (
+      <pre
+        style={{ display: 'inline' }}
+        dangerouslySetInnerHTML={{ __html: Prism.highlight(str, Prism.languages[language], language) }}
+      />
+    );
+  } catch (e) {
+    return <pre style={{ display: 'inline' }}>{str}</pre>;
+  }
 }
 
 export type DiffMode = 'Split' | 'Unified';