fix: ignore checking fragment in own file

We don't need to check if fragments are valid in own file.
It's already checked by the rule MD051 of markdownlint (else we have the error duplicated).
Ref: https://github.com/DavidAnson/markdownlint/blob/main/doc/md051.md

src/index.js

@@ -49,7 +49,9 @@ const customRule = {
         if (hrefSrc != null) {
           const url = new URL(hrefSrc, pathToFileURL(params.name))
           const isRelative =
-            url.protocol === "file:" && !hrefSrc.startsWith("/")
+            url.protocol === "file:" &&
+            !hrefSrc.startsWith("/") &&
+            !hrefSrc.startsWith("#")
           if (isRelative) {
             const detail = `"${hrefSrc}"`