Znk fix 106: update to {matchmaker}

[zkamvar]

• Both clean_variable_spelling() and clean_spelling() have been migrated over
  to the {matchmaker} package and arguments from the aformentioned functions are
  passed to the {matchmaker} functions. Tests and documentation have been
  updated to reflect this.
• Remove {rlang} from imports (but is still imported by {matchmaker}).

[zkamvar]

Note: depending on the order this and #109 are merged, one of these will have to fix a conflict in the version number/news