Allow pre-filling tags in new bookmark form

[dasrecht]

Hi there 👋

I'm moving from another comparable system to linkding and realized that I can't set the bookmarks in custom bookmark snippets. This PR reads tag_string from the GET requests, allowing to pre-fill tags.

Hope that is ok to add it like I've done in the PR. Let me know if there's also some documentation that needs to be amended.

/dasrecht

[sissbruecker]

Makes sense, changed the parameter name to tags though.

[jk]

By the way, I've modified the bookmarklet to also pre-fill a couple of the other fields:

javascript:(function () {
    let w = 580;
    let h = 780;
    let l = Math.floor((screen.width - w) / 2);
    let t = Math.floor((screen.height - h) / 2);
    let u = encodeURIComponent(location.href);
    let s = encodeURIComponent(getSelection().toString());
    let ti = encodeURIComponent(document.title);

    let lnk = `https://linkding.example.tld/bookmarks/new?url=${u}&description=${s}&title=${ti}&auto_close#id_tag_string`;

    window.open(lnk, "Bookmarklet", `width=${w},height=${h},left=${l},top=${t}`);
})();