Fix custom link renderer and add tests for Confluence links

Since we now have a custom parser for <ac:*/> tags, the custom link
renderer added an additional </a> tag at the end of each internal
Confluence link.

Add tests for internal links and add an example for internal links with
spaces in page titles to the README file.

pkg/mark/markdown.go

@@ -276,9 +276,8 @@ func (r *ConfluenceRenderer) renderLink(writer util.BufWriter, source []byte, no
 			if err != nil {
 				return ast.WalkStop, err
 			}
-
-			return ast.WalkSkipChildren, nil
 		}
+		return ast.WalkSkipChildren, nil
 	}
 	return r.goldmarkRenderLink(writer, source, node, entering)
 }

pkg/mark/testdata/links.html

@@ -1,5 +1,9 @@
 <p>Use <a href="https://example.com">https://example.com</a></p>
 <p>Use <ac:rich-text-body>aaa</ac:rich-text-body></p>
+<p>Use <ac:link><ri:page ri:content-title="Page"/><ac:plain-text-link-body><![CDATA[page link]]></ac:plain-text-link-body></ac:link></p>
+<p>Use <ac:link><ri:page ri:content-title="AnotherPage"/><ac:plain-text-link-body><![CDATA[AnotherPage]]></ac:plain-text-link-body></ac:link></p>
+<p>Use <ac:link><ri:page ri:content-title="Another Page"/><ac:plain-text-link-body><![CDATA[Another Page]]></ac:plain-text-link-body></ac:link></p>
+<p>Use <ac:link><ri:page ri:content-title="Page With Space"/><ac:plain-text-link-body><![CDATA[page link with spaces]]></ac:plain-text-link-body></ac:link></p>
 <p>Use footnotes link <sup id="fnref:1"><a href="#fn:1" class="footnote-ref" role="doc-noteref">1</a></sup></p>
 <div class="footnotes" role="doc-endnotes">
 <hr />

pkg/mark/testdata/links.md

@@ -2,5 +2,13 @@ Use <https://example.com>
 
 Use <ac:rich-text-body>aaa</ac:rich-text-body>
 
+Use [page link](ac:Page)
+
+Use [AnotherPage](ac:)
+
+Use [Another Page](ac:)
+
+Use [page link with spaces](<ac:Page With Space>)
+
 Use footnotes link [^1]  
 [^1]: a footnote link