fix: html block regex prefix conflict (#558)

Closes #530

.changeset/two-files-relate.md

@@ -0,0 +1,5 @@
+---
+"markdown-to-jsx": patch
+---
+
+Fix HTML block regex for custom component scenarios where a nested component shares the same prefix as the parent, e.g. Accordion vs AccordionItem.

index.compiler.spec.tsx

@@ -4329,6 +4329,19 @@ describe('overrides', () => {
       </div>
     `)
   })
+
+  it('#530 nested overrides', () => {
+    render(
+      compiler('<Accordion><AccordionItem>test</AccordionItem></Accordion>', {
+        overrides: {
+          Accordion: ({ children }) => children,
+          AccordionItem: ({ children }) => children,
+        },
+      })
+    )
+
+    expect(root.innerHTML).toMatchInlineSnapshot(`"test"`)
+  })
 })
 
 it('should remove YAML front matter', () => {

index.tsx

@@ -254,7 +254,7 @@ const HEADING_SETEXT_R = /^([^\n]+)\n *(=|-){3,} *(?:\n *)+\n/
  *    \n*
  */
 const HTML_BLOCK_ELEMENT_R =
-  /^ *(?!<[a-z][^ >/]* ?\/>)<([a-z][^ >/]*) ?([^>]*)>\n?(\s*(?:<\1[^>]*?>[\s\S]*?<\/\1>|(?!<\1)[\s\S])*?)<\/\1>\n*/i
+  /^ *(?!<[a-z][^ >/]* ?\/>)<([a-z][^ >/]*) ?([^>]*)>\n?(\s*(?:<\1[^>]*?>[\s\S]*?<\/\1>|(?!<\1\b)[\s\S])*?)<\/\1>\n*/i
 
 const HTML_CHAR_CODE_R = /&([a-z0-9]+|#[0-9]{1,6}|#x[0-9a-fA-F]{1,6});/gi