add content type to webhook request

[MajdT51]

Title: Webhook message has no content type

Description: Add the content type to the request header in webhook Issue: https://github.com/hyperledger/aries-framework-go/issues/3158

[codecov[bot]]

Codecov Report

Merging #3159 (a1f4697) into main (4b0d40d) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #3159   +/-   ##
=======================================
  Coverage   87.98%   87.98%           
=======================================
  Files         329      329           
  Lines       45261    45263    +2     
=======================================
+ Hits        39821    39823    +2     
  Misses       4024     4024           
  Partials     1416     1416           

Impacted Files	Coverage Δ
pkg/controller/webnotifier/webhook.go	93.75% <100.00%> (+0.27%)	:arrow_up:

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[sudeshrshetty]

@MajdT51 thanks for your contribution, please rebase your PR

[MajdT51]

@MajdT51 thanks for your contribution, please rebase your PR

Thanks. It's done