Use -PassThru for methods that write to disk and return a value

[bryanbcook]

Certain methods have optional parameters that are used to write results to disk, but these methods also return a value that might not be used.

The following methods should include a -PassThru switch to return the object when writing disk.

• Get-BloggerPost has an optional -Format which is used to persist to disk.
• Publish-MarkdownDriveImages might benefit from this
• ConvertTo-MarkdownFromHtml has an optional -OutFile.
• ConvertTo-HtmlFromMarkdown has an optional -OutFIle that has an automatic default value. -PassThru would make sense here.