feat: Added retry interval sec config

[yottahmd]

Added interval sec config to retryPolicy.

Example:

steps:
  - name: task1
    command: main.py
    retryPolicy:
      limit: 2
      intervalSec: 5

[codecov-commenter]

Codecov Report

Merging #181 (450396b) into main (d065233) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #181      +/-   ##
==========================================
+ Coverage   82.79%   82.86%   +0.06%     
==========================================
  Files          40       40              
  Lines        2999     3011      +12     
==========================================
+ Hits         2483     2495      +12     
  Misses        392      392              
  Partials      124      124              

Impacted Files	Coverage Δ
internal/config/step.go	0.00% <ø> (ø)
internal/config/config.go	83.62% <100.00%> (+0.04%)	⬆️
internal/scheduler/node.go	89.30% <100.00%> (+0.41%)	⬆️
internal/scheduler/scheduler.go	85.71% <100.00%> (+0.14%)	⬆️

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