`const: {since}` links broken or removed by the extension

[ian-h-chamberlain]

Thanks for this extension! I initially thought this was a bug in rustdoc but after some investigation realized this extension was rewriting doc links.

Since const stability often has a different version than stability, it would be nice to provide separate links for the different versions.

Example reformatted for readability, without the extension enabled (stable 1.33.0, const unstable (already links to stability issue):

<span class="since" title="Stable since Rust version 1.33.0, const unstable">
    1.33.0 (const:
    <a href="https://github.com/rust-lang/rust/issues/91930" title="Tracking issue for const_option_ext">
       unstable
    </a>
    )
</span>

This gets rewritten by the extension to

<span class="since" title="const unstable">
    <a class="rse-link" href="https://github.com/rust-lang/rust/blob/master/RELEASES.md?version=const: unstable">
        const: unstable
    </a>
</span>

But I think the links should be preserved like

<span class="since" title="Stable since Rust version 1.33.0, const unstable">
    <a class="rse-link" href="https://github.com/rust-lang/rust/blob/master/RELEASES.md?version=1.33.0">
        1.33.0
    </a>
    (const:
    <a href="https://github.com/rust-lang/rust/issues/91930" title="Tracking issue for const_option_ext">
        unstable
    </a>
    )
</span>

---

Example 2 without extension:

<span class="since" title="Stable since Rust version 1.10.0, const since 1.72.0">
    1.10.0 (const: 1.72.0)
</span>

This is rewritten to

<span class="since" title="Stable since Rust version 1.10.0, const since 1.72.0">
    <a class="rse-link" href="https://github.com/rust-lang/rust/blob/master/RELEASES.md?version=1.10.0">
        1.10.0 (const: 1.72.0)
    </a>
</span>

But something like would be preferable:

<span class="since" title="Stable since Rust version 1.10.0, const since 1.72.0">
    <a class="rse-link" href="https://github.com/rust-lang/rust/blob/master/RELEASES.md?version=1.10.0">
        1.10.0
    </a>
    (const:
    <a class="rse-link" href="https://github.com/rust-lang/rust/blob/master/RELEASES.md?version=1.72.0">
        1.72.0
    </a>
    )
</span>

[Folyd]

Thanks for the feedback. I guess I forgot to remove this const: {since} links feature. I'll remove it it the next version. :)