chore: add go tool tip to makefile

[RafilxTenfen]

Description

• Add go tip to the makefile to generate easily readable coverage
• run make test-unit-cover
• open it in the browser with go tool cover -html=coverage.txt
  

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Author Checklist

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I have...

• included the correct type prefix in the PR title
• added appropriate labels to the PR
• added ! to the type prefix if API or client breaking change
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• added a changelog entry to CHANGELOG.md
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• updated the relevant documentation or specification
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• confirmed the correct type prefix in the PR title
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• reviewed state machine logic
• reviewed API design and naming
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[RafilxTenfen]

@toteki Maybe we could add it as a new command in the make and check if exists the coverage.txt file, if not runs test-unit-cover first

What do you think ?

[toteki]

make cover-html perhaps?

And probably have it run test-unit-cover always in case changes have been made.