feat: Add optional field group to organize DAGs on Web UI

[yottahmd]

Add an optional field group to organize DAGs on Web UI.

Example:

group: Utility
steps:
  - name: hello
     command: echo hello

[codecov-commenter]

Codecov Report

Merging #182 (c503436) into main (7dc9f49) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #182   +/-   ##
=======================================
  Coverage   82.86%   82.86%           
=======================================
  Files          40       40           
  Lines        3011     3012    +1     
=======================================
+ Hits         2495     2496    +1     
  Misses        392      392           
  Partials      124      124           

Impacted Files	Coverage Δ
internal/config/config.go	83.66% <100.00%> (+0.04%)	⬆️

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