Added API versioning support (#379)

GitHub is introducing versioned API's.  In order to get the expected behavior of an API, you need to invoke the API with its version in the request header.  This change updates the core functions (`Invoke-GHRestMethod` and `Invoke-GHRestMethodMultipleResult`) to accept an ApiVersion as part of their param sets so that as the module continues to add new functionality, methods can request the appropriate API Version for their individual calls.

Fixes #377 

Reference: [To infinity and beyond: enabling the future of GitHub’s REST API with API versioning](https://github.blog/2022-11-28-to-infinity-and-beyond-enabling-the-future-of-githubs-rest-api-with-api-versioning/)
[API Versions](https://docs.github.com/en/rest/overview/api-versions?apiVersion=2022-11-28)

Author: variableresistor

CONTRIBUTING.md

@@ -614,6 +614,7 @@ Thank you to all of our contributors, no matter how big or small the contributio
 - **[Giuseppe Campanelli (@themilanfan)](https://github.com/themilanfan)**
 - **[Christoph Bergmeister (@bergmeister)](https://github.com/bergmeister)**
 - **[Simon Heather (@X-Guardian)](https://github.com/X-Guardian)**
+- **[Neil White (@variableresistor)](https://github.com/variableresistor)**
 
 ----------
 

GitHubCore.ps1

@@ -80,6 +80,9 @@ function Invoke-GHRestMethod
         If specified, this will save the result to a temporary file and return the FileInfo of that
         temporary file.
 
+    .PARAMETER ApiVersion
+         Indicates the version of this API that should be used. Format is: 'yyyy-MM-dd'.
+
     .PARAMETER AccessToken
         If provided, this will be used as the AccessToken for authentication with the
         REST Api as opposed to requesting a new one.
@@ -145,6 +148,9 @@ function Invoke-GHRestMethod
 
         [switch] $Save,
 
+        [ValidatePattern('^\d{4}-\d{2}-\d{2}$')]
+        [string] $ApiVersion = "2022-11-28",
+
         [string] $AccessToken,
 
         [string] $TelemetryEventName = $null,
@@ -232,6 +238,7 @@ function Invoke-GHRestMethod
     $headers = @{
         'Accept' = $AcceptHeader
         'User-Agent' = 'PowerShellForGitHub'
+        'X-GitHub-Api-Version' = $ApiVersion
     }
 
     # Add any additional headers
@@ -609,6 +616,9 @@ function Invoke-GHRestMethodMultipleResult
         Allows the caller to specify any number of additional headers that should be added to
         all of the requests made.
 
+    .PARAMETER ApiVersion
+         Indicates the version of this API that should be used. Format is: 'yyyy-MM-dd'.
+
     .PARAMETER AccessToken
         If provided, this will be used as the AccessToken for authentication with the
         REST Api as opposed to requesting a new one.
@@ -660,6 +670,9 @@ function Invoke-GHRestMethodMultipleResult
 
         [hashtable] $AdditionalHeader = @{},
 
+        [ValidatePattern('^\d{4}-\d{2}-\d{2}$')]
+        [string] $ApiVersion = "2022-11-28",
+
         [string] $AccessToken,
 
         [string] $TelemetryEventName = $null,
@@ -700,6 +713,7 @@ function Invoke-GHRestMethodMultipleResult
                 'AcceptHeader' = $AcceptHeader
                 'AdditionalHeader' = $AdditionalHeader
                 'ExtendedResult' = $true
+                'ApiVersion' = $ApiVersion
                 'AccessToken' = $AccessToken
                 'TelemetryProperties' = $telemetryProperties
                 'TelemetryExceptionBucket' = $errorBucket