doc(README) : add prerequisites

[adriens]

:grey_question: About

While trying to play with ollama-python on a brand new env, I found out that following the current steps of the README do not take in account that ollama must be up and running (ie. that it's not ollama-python role).

:dart: Objective

The purpose of this PR is to make the Getting started even easier to people can just copy/paste and enjoy :smile:

[adriens]

:pray: @mikeesto for the code suggestion :smile_cat:

[mak448a]

This would close #29.

[connor-makowski]

Worth mentioning that there are a few ways to do this. For example, you might also add something like:

## Local Ollama Setup
You need to have a local ollama server running to be able to continue. To do this:

- Download: https://ollama.com/
- Run an LLM: https://ollama.com/library
    - Example: `ollama run llama2`
    - Example: `ollama run llama2:70b`

[adriens]

:pray: @connor-makowski

[haesleinhuepf]

Big thanks @adriens

[adriens]

Big thanks @adriens

That was a very modest contribution, but it's always very cool to get feedbacks from projects you really enjoy a lot working with :star_struck: @haesleinhuepf

[haesleinhuepf]

Dear maintainers,

this is a very useful documentation update. Consider merging it. 😉

[adriens]

:partying_face:

[adriens]

Tweet

[connor-makowski]

Referencing this to: https://github.com/ollama/ollama-python/pull/155 as an extension for adding clarity to the getting started process.