Updated model docs

[LeonArmston]

Hi @jameseccles

I've made some changes to the models folders and readme files.

• Added Assets folder to each model to include an image of a example training file
• Added training files to a /training-files folder in each model
• Updated README.md to show example image preview of example training file
• Deleted Invoice Processing model as this now appears in Scenario Samples folder.
• Fixed PnP Reporting 1px image location as was pointing to previous /samples folder rather than the now renamed /models folder
• Renamed folders to replace spaces with dashes

Renamed folders to remove spaces is part of a longer goal to add a web front end to this repo. I've got it compiling all using DocFX which turns the markdown files into html files (see below)

It would be great to talk to @jansenbe if possible who has created a web from end for the M365 Assessment tool which I based my creation/index files on and requires everything to be moved into a docs folder (for the website). Once this is merged I'll create an Issue to work on the web front end for syntex-samples i.e. https://pnp.github.com/syntex-samples

[jameseccles]

Thanks @LeonArmston , this is great.

@Spucelik - a quick check- are you good with deleting the Invoice model from the samples folder? I think your solution sample now uses the prebuilt, so this is redundant?

Once confirmed, I'll merge.