docs: Update NuGet badges (Release 5.x)

[Dor-bl]

Change list

Add Build and Deploy NuGet badge + Change Nuget to use pre-release which is the only one relevant for 5.x branch

Types of changes

What types of changes are you proposing/introducing to .NET client?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• New feature (non-breaking change which adds value to the project)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Documentation

• Have you proposed a file change/ PR with appium to update documentation?

This can be done by navigating to the documentation section on http://appium.io selecting the appropriate command/endpoint and clicking the 'Edit this doc' link to update the C# example

Integration tests

• Have you provided integration tests to pass against the beta version of appium? (for Bugfix or New feature)

Details

Please provide more details about changes if it is necessary. If there are new features you can provide code samples which show the way they
work and possible use cases. Also you can create gists with pasted C# code samples or put them here using markdown.
About markdown please read Mastering markdown and Writing on GitHub

[KazuCocoa]

btw, can we make this 5.x as stable release...?

[Dor-bl]

@KazuCocoa, Last time I discussed this option with @laolubenson he said we first need to add more docs for that release, I Still haven't got the time.
also, I'm not sure the best approach to replace the master with the 5.x. (I'm still finding my way through GitHub)
Should we delete the master branch and rename release/5.0.0 to main?
Maybe we should first release an RC version?

[laolubenson]

@KazuCocoa, Last time I discussed this option with @laolubenson he said we first need to add more docs for that release, I Still haven't got the time.

also, I'm not sure the best approach to replace the master with the 5.x. (I'm still finding my way through GitHub)

Should we delete the master branch and rename release/5.0.0 to main?

Maybe we should first release an RC version?

Yeah, perhaps we should put a date on it, cut and release for example on September 1st.

[KazuCocoa]

Sounds good to me.
For the branching, we could stay the current master as a new name such as v4 branch for example, and make the 5.0 as main like https://github.com/appium/appium 's master -> v1 and v2 -> master

[Dor-bl]

I created a milestone for 5.0.0-rc1
unless you guys want to skip the rc step