fix(barchart): divide by zero in render

[joshka]

• fix(table): add default column widths for when none are supplied
• implement suggestions in comments
• add docs, correct length calculation
• simplify logic in constructing constraints
• add docs to public methods
• fix overflow panic
• fix(barchart): avoid divide by zero in rendering

[joshka]

This wasn't meant to have a copy of the table branches in it, just the barchart. rebased

[codecov]

Codecov Report

Merging #525 (9362015) into main (be55a5f) will increase coverage by 0.00%.
The diff coverage is 94.11%.

@@           Coverage Diff           @@
##             main     #525   +/-   ##
=======================================
  Coverage   90.01%   90.01%           
=======================================
  Files          40       40           
  Lines       11193    11209   +16     
=======================================
+ Hits        10075    10090   +15     
- Misses       1118     1119    +1     

Files Changed	Coverage Δ
src/widgets/barchart.rs	92.96% <94.11%> (+0.01%)	⬆️