Add package with build tasks to format on build

[shocklateboy92]

My coworkers are (pretty much) guaranteed forget to run the dotnet tool command, so I want to run it for them automatically during build.

This creates a nuget package that injects a build task that formats before build. Assuming you're fine with the approach, you'll need to update the metadata of the package and update the github actions to publish it too.

[belav]

As someone who is guilty of forgetting to prettier my files all the time at work without a file watcher, I love it.

Personally, I'd want to run this for debug, and then run it with --check during release. Although doing the --check as a build step might be a little weird because it makes it harder for someone to run release code locally.

My original thought was we should add some properties to support situations like that.

<PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
  <CSharpier_Disable>true</CSharpier_Disable>// maybe CSharpier_Enable?
  <CSharpier_Check>true</CSharpier_Check>
</PropertyGroup>

On the other hand you can always run the check as a separate github action, like .github/workflows/validatePR.yml, so maybe we don't need to worry about adding properties right now.

I believe this depends on #181 to support .csharpierrc and .csharpierignore, which I was going to work on in the next day or two.

[belav]

I think this is what is needed to publish the msbuild project. I haven't tested out trying to reference this nuget package in a project yet.
The readme should also get updated, but I'm about to split that apart

[shocklateboy92]

You need the netstandard2.0 here. Otherwise it can't be used to format projects that don't also target net5.0 themselves

[belav]

closes #218