readme new user updates

[jabelk]

Hi!

First off, great job on the documentation and project! Really well done in terms of technology choices and usability. It was super simple to get up and going with Docker / Poetry / Invoke.

When I was following the README installing with Docker Compose Nautobot, I noticed a few minor improvements that could be made. Feel free to use other verbiage or other ways of solving the same issue.

Basically 2 things about the install process could be improved:

Main README

1. Going through the README top to bottom, I ensured Docker, Poetry and Invoke were installed, which had great instructions. Then after reading ## Install Poetry, I assumed the next step was ## Build and start Nautobot and was confused why things were not working, especially with the phrase Nautobot will be available on port 8080 locally http://localhost:8080, I assumed I had done something wrong.

I then realized after scrolling through several more subsections, after doing some troubleshooting that there was a full ## Getting Started section that I didn't see and included important steps like copying the .env files and such. Once I followed those steps everything worked well.

In order to call attention to the Getting Started part, I added some explanation early on ## How to use this repo part, though including a table of contents to show people that the Getting Started part is way far down the README is another option.

2. After getting the app installed, I couldn't authenticate. I was confused because in the getting started guide the credential files I copied seemed to have usernames and passwords in them. I saw at the end ## Super User Account, but did not realize it was a required step if I wanted to authenticate into the app.

For the sake of clarity, I added a phrase at the beginning of that section to let people know this is required if you are testing locally, the credential files are not enough.

[jdrew82]

Thank you for this contribution! I'm wanting to refresh the documentation with a focus on the Diataxis pattern to hopefully make things easier to understand. These bits are certainly a help so thanks! Just a small question on one part and we can get it merged.