feat(option): support priority for highlight

[younger-1]

Description

Added support for setting priority of each highlight. This is needed when users want to override/reserve highlights of semantic tokens or treesitter, which may have higher/lower priority than paint.nvim's default value.

Related Issue(s)

Screenshots

Before (without set priority):

After (set priority to 999):

[github-actions[bot]]

This PR is stale because it has been open 30 days with no activity.