text: Title: [DOC] add common unequal length and multivariate patterns to the classification tutorial
  Body: Newer patterns to handle unequal length and multivariate data should be added to the classification tutorial.
  
  * handling multivariate data using the "sum of independent distances" approach and arithmetic combinations - `IndepDist`
  * handling multivariate data by constructing univariate distances on individual components and combining them - `CombinedDistance` and variable subsetting
  * handling unequal length data by using custom distances that are valid for unequal length time series, see here: https://github.com/sktime/sktime/discussions/7232
  
  The appropriate place might be the sections already discussing multivariate and unequal length data, if exists, otherwise a good place should be found.