Update module to be able to specify the default branch name for a repository

Issue Details

GitHub is moving forward with a plan to start changing the name of the default branch from being master to main (although this can also be further configurable).

At this time, we only have some tests that expect that the default branch name is master. We should keep an eye on the API to see when it gets updated so that we can either specify what the default branch name should be for a repository on a per-repository basis, or for the account as a whole.

When last checked, this was not yet possible via the API.

Requested Assignment

I'm just reporting this problem, but don't want to fix it.

Operating System

OsName               : Microsoft Windows 10 Pro
OsOperatingSystemSKU : 48
OsArchitecture       : 64-bit
WindowsVersion       : 1909
WindowsBuildLabEx    : 18362.1.amd64fre.19h1_release.190318-1202
OsLanguage           : en-US
OsMuiLanguages       : {en-US}

PowerShell Version

Name                           Value
----                           -----
PSVersion                      5.1.18362.752
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.18362.752
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Module Version

Running: 0.14.0
Installed: