[docs-infra] Skip non React components in visual regressions (#41708)

test/regressions/index.js

@@ -31,7 +31,6 @@ const blacklist = [
   'docs-getting-started-templates-sign-in/CustomIcons.png', // Theme file
   'docs-getting-started-templates-sign-up/CustomIcons.png', // Theme file
   'docs-getting-started-templates-sign-in-side/getSignInSideTheme.png', // Theme file
-  'docs-getting-started-templates-sign-in/getSignInTheme.png', // Theme file
   'docs-getting-started-templates-sign-up/getSignUpTheme.png', // Theme file
   'docs-getting-started-templates-checkout/getCheckoutTheme.png', // Theme file
   'docs-getting-started-templates-landing-page/getLPTheme.png', // Theme file
@@ -173,6 +172,13 @@ function excludeDemoFixture(suite, name) {
     return true;
   }
 
+  // Exclude files that are not images and are not PascalCase
+  // Tantamount to skipping JS/TS files that are not React components or "index.js" files
+  // PascalCase starts with a capital letter and has zero or more capital letters in the middle
+  if (!suite.endsWith('.png') && name !== 'index' && !/^[A-Z][A-Za-z0-9]*$/.test(name)) {
+    return true;
+  }
+
   if (suite.includes('docs-joy') && name.match(/(Variables|Usage)$/)) {
     return true;
   }