Missing identifier with Markdown in the name gets weirdly transformed

[oprypin]

Given the input [*Foo-bar*][] with no such matching identifier, the output is [<em>Foo-bar</em>][*Foo-bar*] but ideally it would be [*Foo-bar*][] or at least [<em>Foo-bar</em>][].

See https://github.com/mkdocstrings/autorefs/pull/5#discussion_r617119616