chore: log error details on --debug flag enabled (#511)

Author: JounQin

.changeset/poor-lions-buy.md

@@ -0,0 +1,5 @@
+---
+"eslint-mdx": patch
+---
+
+chore: log error details on `--debug` flag enabled

packages/eslint-mdx/src/parser.ts

@@ -62,6 +62,10 @@ export class Parser {
         ignoreRemarkConfig,
       })
     } catch (err: unknown) {
+      /* istanbul ignore if */
+      if (process.argv.includes('--debug')) {
+        console.error(err)
+      }
       const error = err as VFileMessage
       throw Object.assign(
         new SyntaxError(error.message, {