Watch method to track config file changes

[DenisPalnitsky]

Add Watch method reloads the config struct every time config file has changed.
This functionality does not work for environment variables as they are kind of designed to stay unchanged for a running process.

[codecov-commenter]

Codecov Report

Patch coverage: 63.15% and project coverage change: -1.64% ⚠️

Comparison is base (d717df0) 85.22% compared to head (dbb6344) 83.58%.

❗ Your organization is not using the GitHub App Integration. As a result you may experience degraded service beginning May 15th. Please install the Github App Integration for your organization. Read more.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   85.22%   83.58%   -1.64%     
==========================================
  Files           1        1              
  Lines         176      195      +19     
==========================================
+ Hits          150      163      +13     
- Misses         18       22       +4     
- Partials        8       10       +2     

Flag	Coverage Δ
unittests	83.58% <63.15%> (-1.64%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
config.go	83.58% <63.15%> (-1.64%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.