README: highlight technical and brand terms

[achille-roussel]

This issue is a follow-up to the feedback we got on the Python SDK, in particular:

One (opinionated) suggestion I would make would be to highlight the Dispatch terms, e.g. in bold or italic text, to make it clear that it's a product specific term (or maybe is a computer science term I never saw, but anyway). For example, "durable coroutine", or "stateful function". And I would try to clearly add definitions for those terms.

This is not about changing the content but simply improving the form of our documentation, the intent being to guide readers through the text better.