Add new semantic token types

[bstaletic]

PR Prelude

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Why this change is necessary and useful

The decorator type was introduced in LSP 1.17. The concept type is used by clangd.

Reported by @amosnier on gitter. The mapped value is just the first thing that came to my mind. Feel free to suggest bette alternatives.

[Please explain in detail why the changes in this PR are needed.]

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This change is