Clarify docs: deltaLine and deltaStart fields of semantic tokens relate to the _start_ of the previous token

[StachuDotNet]

In writing an LSP-based language server, I've recently fumbled for a while assuming that these fields related to the end of any previous token. The highlighting just wasn't working the way I expected to, because of this assumption.

I now understand why the format is the way it is - to support overlapping tokens, in the languages those are relevant, but this wasn't obvious to me.

I'd be happy to update relevant pieces of docs via PRs.

I know of 2 relevant places to update:

• [x] in these lines of the spec:

  at index 5*i - deltaLine: token line number, relative to the previous token
  at index 5*i+1 - deltaStart: token start character, relative to the previous token (relative to 0 or the previous token’s start if they are on the same line)

  (simply adding wording like "relative to the start of the previous token...")

• [ ] the de facto Node sample

any other places that would be useful to clarify in?

[dbaeumer]

Looks good to me.

[StachuDotNet]

Thanks for the response, I'll get to it tonight.

[StachuDotNet]

Finally got around to this in #1966 - I thought there'd be mention of deltaLine and such in vscode-languageserver-node as well, but seems not.