Function splitAndUpdateRuns

splitAndUpdateRuns(runs, update, onUpdate?): ModifiedRuns<any>
Split/update algo used for formatted text. This will split and update runs

All runs must be: ** ordered ** non-overlapping Runs do not need to be contiguous.
Parameters
- runs: Run<any>[]
- update: Run<any>
- Optional onUpdate: ((prevValue, newValue, run) => any)
  - - (prevValue, newValue, run): any
    - Parameters
      prevValue: any
      newValue: any
      run: Run<any>
      Returns any
Returns ModifiedRuns<any>