fix content-type for hydra commits / add headers

[VladislavKudrin]

Summary

Axios sets "Content-Type": "application/json", which triggers a CORS preflight in buildCommit.

Affect components

• @meshsdk/common
• @meshsdk/contract
• @meshsdk/core
• @meshsdk/core-csl
• @meshsdk/core-cst
• @meshsdk/hydra
• @meshsdk/provider
• @meshsdk/react
• @meshsdk/svelte
• @meshsdk/transaction
• @meshsdk/wallet
• Mesh playground (i.e. https://meshjs.dev/)
• Mesh CLI

Type of Change

Please mark the relevant option(s) for your pull request:

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bug fix (non-breaking change which fixes an issue)
• Code refactoring (improving code quality without changing its behavior)
• Documentation update (adding or updating documentation related to the project)

Checklist

Please ensure that your pull request meets the following criteria:

• My code is appropriately commented and includes relevant documentation, if necessary
• I have added tests to cover my changes, if necessary
• I have updated the documentation, if necessary
• All new and existing tests pass (i.e. npm run test)
• The build is pass (i.e. npm run build)