loader: add plain text mime type

Co-authored-by: pdeveltere <pdeveltere@users.noreply.github.com>

Author: efekrskl

lib/internal/modules/esm/get_format.js

@@ -47,6 +47,13 @@ function mimeToFormat(mime) {
   ) { return 'module'; }
   if (mime === 'application/json') { return 'json'; }
   if (mime === 'application/wasm') { return 'wasm'; }
+  if (
+    getOptionValue('--experimental-import-text') &&
+    RegExpPrototypeExec(
+      /^\s*text\/plain\s*(;\s*charset=utf-?8\s*)?$/i,
+      mime,
+    ) !== null
+  ) { return 'text'; }
   return null;
 }
 

test/es-module/test-esm-import-text.mjs

@@ -42,7 +42,7 @@ assert.match(jsonAsText.default, /"im broken"/);
 
 await assert.rejects(
   import('data:text/plain,hello%20world'),
-  { code: 'ERR_UNKNOWN_MODULE_FORMAT' },
+  { code: 'ERR_IMPORT_ATTRIBUTE_MISSING' },
 );
 
 await assert.rejects(