Update MD040/fenced-code-language to add allowed_languages parameter (fixes #610).

test/snapshots/markdownlint-test-scenarios.js.md

@@ -29318,6 +29318,87 @@ Generated by [AVA](https://avajs.dev).
       `,
     }
 
+## md040-allowed_languages.md
+
+> Snapshot 1
+
+    {
+      errors: [
+        {
+          errorContext: null,
+          errorDetail: '"html" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 5,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md040',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
+        {
+          errorContext: null,
+          errorDetail: '"css" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 11,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md040',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
+      ],
+      fixed: `# md040-allowed_languages.md␊
+      ␊
+      Code block with \`html\` not in allowed_languages:␊
+      ␊
+      \`\`\`html␊
+      <h1>markdownlint</h1> {MD040:5}␊
+      \`\`\`␊
+      ␊
+      Code block with \`css\` not in allowed_languages:␊
+      ␊
+      \`\`\`css␊
+      body {}  {MD040:11}␊
+      \`\`\`␊
+      ␊
+      Code block with \`js\` in allowed_languages:␊
+      ␊
+      \`\`\`js␊
+      console.log('markdownlint')␊
+      \`\`\`␊
+      ␊
+      Code block with \`scss\` in allowed_languages:␊
+      ␊
+      \`\`\`scss␊
+      body {␊
+        h1 {␊
+          color: red;␊
+        }␊
+      }␊
+      \`\`\`␊
+      ␊
+      Code block with \`md\` in allowed_languages:␊
+      ␊
+      \`\`\`MD␊
+      hello md␊
+      \`\`\`␊
+      ␊
+      Code block with \`TS\` in allowed_languages:␊
+      ␊
+      \`\`\`ts␊
+      body {␊
+        h1 {␊
+          color: red;␊
+        }␊
+      }␊
+      \`\`\`␊
+      `,
+    }
+
 ## md041-ignore-leading-comments-combined.md
 
 > Snapshot 1