Update MD040/fenced-code-language to use case-sensitive comparison for allowed languages (fixes #627).

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

@@ -29324,6 +29324,26 @@ Generated by [AVA](https://avajs.dev).
 
     {
       errors: [
+        {
+          errorContext: '` scss`',
+          errorDetail: null,
+          errorRange: [
+            17,
+            7,
+          ],
+          fixInfo: {
+            deleteCount: 5,
+            editColumn: 18,
+            insertText: 'scss',
+          },
+          lineNumber: 39,
+          ruleDescription: 'Spaces inside code span elements',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md038.md',
+          ruleNames: [
+            'MD038',
+            'no-space-in-code',
+          ],
+        },
         {
           errorContext: null,
           errorDetail: '"html" is not allowed',
@@ -29350,6 +29370,32 @@ Generated by [AVA](https://avajs.dev).
             'fenced-code-language',
           ],
         },
+        {
+          errorContext: null,
+          errorDetail: '"MD" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 17,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md040.md',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
+        {
+          errorContext: null,
+          errorDetail: '"ts" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 23,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md040.md',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
       ],
       fixed: `# md040-allowed_languages.md␊
       ␊
@@ -29365,15 +29411,33 @@ Generated by [AVA](https://avajs.dev).
       body {}  {MD040:11}␊
       \`\`\`␊
       ␊
+      Code block with \`MD\` (uppercase) not in allowed_languages:␊
+      ␊
+      \`\`\`MD␊
+      hello md {MD040:17}␊
+      \`\`\`␊
+      ␊
+      Code block with \`ts\` (lowercase) not in allowed_languages:␊
+      ␊
+      \`\`\`ts␊
+      let foo = "bar"; {MD040:23}␊
+      \`\`\`␊
+      ␊
       Code block with \`js\` in allowed_languages:␊
       ␊
       \`\`\`js␊
       console.log('markdownlint')␊
       \`\`\`␊
       ␊
-      Code block with \`scss\` in allowed_languages:␊
+      Code block with \`js foo\` allowed_languages:␊
       ␊
-      \`\`\`scss␊
+      \`\`\`js foo␊
+      console.log('bar')␊
+      \`\`\`␊
+      ␊
+      Code block with \`scss\` (prefixed by a space) in allowed_languages: {MD038}␊
+      ␊
+      \`\`\` scss␊
       body {␊
         h1 {␊
           color: red;␊
@@ -29381,15 +29445,15 @@ Generated by [AVA](https://avajs.dev).
       }␊
       \`\`\`␊
       ␊
-      Code block with \`md\` in allowed_languages:␊
+      Code block with \`md\` (lowercase) in allowed_languages:␊
       ␊
-      \`\`\`MD␊
+      \`\`\`md␊
       hello md␊
       \`\`\`␊
       ␊
-      Code block with \`TS\` in allowed_languages:␊
+      Code block with \`TS\` (uppercase) in allowed_languages:␊
       ␊
-      \`\`\`ts␊
+      \`\`\`TS␊
       body {␊
         h1 {␊
           color: red;␊