Various issues/wishes

[borkdude]

• [x] :hide-columns causes index out of bounds exception
• [x] selecting value in grouped column always yields 0 results (needs repro)
• [x] grouped header is gone
• [x] Noticed another nit pick issue: there is an empty bar for values in-between 1 and 2 here (PARKED)
• [x] :computed-columns option to provide derived columns
• [x] feature to support pre-processing of columns before calculating stats on them

Repro of second issue:

(clerk/with-viewer table-stats/viewer
  {::clerk/width :full
   ::clerk/render-opts {:group-headers true
                        :translated-keys {:hello  "hello"
                                          :bye/go  "1"
                                          :bye/do  "2"}}}
  [{:hello 1 :bye {:go 2 :do 3}}
   {:hello 1 :bye {:go 2 :do 3}}
   {:hello 1 :bye {:go 2 :do 3}}
   {:hello 1 :bye {:go 4 :do 3}}])