LSP server responds to Goto Definition request with LocationLink[] even if the client doesn't support it

[groszdaniel]

Describe the bug
svelte-language-server responds to a Goto Definition request with LocationLink[] even if the client does not report the textDocument.definition.linkSupport capability.

I quote the comment of a developer of a client (Kate):

As for it not working (and the Url turning empty), that is actually a server-side problem. As specified (https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_definition) the reply to a 'textDocument/definition') can be one of Location, or Location[] or LocationLink[]. However, the latter depends on the client specifying it is so capable (which allows extending the protocol without surprising existing client). As it stands, the client does not support that reply nor does it claim to in reported capabilities, so the server should not resort to sending that type of reply.

It's not difficult to extend parsing to handle that reply as well (and will likely do so in the coming days), but such is the background of the situation.

To Reproduce
The language server is run with
node /usr/local/lib/node_modules/svelte-language-server/bin/server.js --stdio
I attach the server's standard streams (stdin, stdout, stderr) and the source files involved (import.html, export.js).

I used "Go to Definition" on the word 'constant' in import.html, while using the Svelte language server. The issue also happens with Svelte files.

System (please complete the following information):

• OS: Linux, openSUSE Tumbleweed
• IDE: Kate 20.8.1
• Plugin/Package: svelte-language-server, LSP Client plugin