GitHubRepositories: Add Get/Set/Remove GitHub Repository Team Permissions (#300)

Adds the following functions:

* `Get-GitHubRepositoryTeamPermission`
* `Set-GitHubRepositoryTeamPermission`
* `Remove-GitHubRepositoryTeamPermission`

References
* [Check team permissions for a repository](https://docs.github.com/en/free-pro-team@latest/rest/reference/teams#check-team-permissions-for-a-repository)
* [Add or update team repository permissions](https://docs.github.com/en/free-pro-team@latest/rest/reference/teams#add-or-update-team-repository-permissions)
* [Remove a repository from a team](https://docs.github.com/en/free-pro-team@latest/rest/reference/teams#remove-a-repository-from-a-team)

Resolves #307

Author: X-Guardian

Formatters/GitHubRepositories.Format.ps1xml

@@ -204,5 +204,29 @@
         </ListEntries>
       </ListControl>
     </View>
+    <!--=============== GitHub.RepositoryTeamPermission Type View ===============-->
+    <View>
+      <Name>GitHub.RepositoryTeamPermission</Name>
+      <ViewSelectedBy>
+        <TypeName>GitHub.RepositoryTeamPermission</TypeName>
+      </ViewSelectedBy>
+      <TableControl>
+        <TableRowEntries>
+          <TableRowEntry>
+            <TableColumnItems>
+              <TableColumnItem>
+                <PropertyName>RepositoryName</PropertyName>
+              </TableColumnItem>
+              <TableColumnItem>
+                <PropertyName>TeamName</PropertyName>
+              </TableColumnItem>
+              <TableColumnItem>
+                <PropertyName>Permission</PropertyName>
+              </TableColumnItem>
+            </TableColumnItems>
+          </TableRowEntry>
+        </TableRowEntries>
+      </TableControl>
+    </View>
   </ViewDefinitions>
 </Configuration>

GitHubCore.ps1

@@ -15,6 +15,7 @@
     mercyAcceptHeader = 'application/vnd.github.mercy-preview+json'
     mockingbirdAcceptHeader = 'application/vnd.github.mockingbird-preview'
     nebulaAcceptHeader = 'application/vnd.github.nebula-preview+json'
+    repositoryAcceptHeader = 'application/vnd.github.v3.repository+json'
     sailorVAcceptHeader = 'application/vnd.github.sailor-v-preview+json'
     scarletWitchAcceptHeader = 'application/vnd.github.scarlet-witch-preview+json'
     squirrelGirlAcceptHeader = 'application/vnd.github.squirrel-girl-preview'