feat: Add dotnet custom template for project and policy boostraping

[Mielek]

Closes #72

Installation:
dotnet new install Azure.ApiManagement.PolicyToolkit.Templates

Success: Azure.ApiManagement.PolicyToolkit.Templates::0.0.1 installed the following templates:
Template Name                                          Short Name             Language  Tags
-----------------------------------------------------  ---------------------  --------  ---------------------------
Azure API Management Policy Toolkit solution template  policytoolkitsolution  [C#]      Solution/Policy Toolkit
Policy Toolkit Policy Class                            policytoolkitclass     [C#]      Policy Toolkit/Policy/Class

Added two templates

1. Solution template - creates a solution with source and test projects. Adds creates dotnet-tools.json with compiler. This template does not contain any template parameters
2. Policy class template - creates class for policy. Allows file and class rename. It can generate section methods e.g. dotnet new policytoolkitclass --name=SomeApiPolicy --Sections=Inbound --Sections=Outbound

Also closes #22 as integration will be done with the existing APIM VS Code extension and templates here should enable easy creation of solution and policy class there.