[eclipse-theiaGH-9882] Add missing completion kind for monaco in plugin

[AirSeeker]

What it does

This PR:

Add missing CompletionItemKind to packages\plugin-ext\src\common\plugin-api-rpc-model.ts

Closes #9882.

How to test

The testing steps are described in #9882.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

@AirSeeker thank you for your contribution.

I can confirm that the issue exists on master and is addressed by the changes nicely 👍

[vince-fugnitto]

The changes look good to me, it matches what we have under node_modules/@theia/monaco-editor-core/monaco.d.ts:

export enum CompletionItemKind {
    Method = 0,
    Function = 1,
    Constructor = 2,
    Field = 3,
    Variable = 4,
    Class = 5,
    Struct = 6,
    Interface = 7,
    Module = 8,
    Property = 9,
    Event = 10,
    Operator = 11,
    Unit = 12,
    Value = 13,
    Constant = 14,
    Enum = 15,
    EnumMember = 16,
    Keyword = 17,
    Text = 18,
    Color = 19,
    File = 20,
    Reference = 21,
    Customcolor = 22,
    Folder = 23,
    TypeParameter = 24,
    User = 25,
    Issue = 26,
    Snippet = 27
}