add introduction --> core-concepts/how-do-aeas-create-value

[FelixNicolaeBucsa]

Proposed changes

Added how do AEAs create value section in introduction

Issues

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• [ ] Bugfix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to stop working as expected)
• [ ] Something else (e.g. test, package, script, example, deployment, infrastructure, ...)

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• [x] I have read the CONTRIBUTING document.
• [x] I have based my branch, and I am making a pull request against, the develop branch.
• [ ] Lint and unit tests pass locally with my changes.

If applicable

• [ ] I have added tests that prove my fix is effective or that my feature works.
• [ ] I have checked that code coverage does not decrease.
• [ ] I have added/updated the documentations.
• [ ] Dependent changes have been merged and published in downstream modules.

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