For Indexes Included Fields, please list 'unformatted' version if Markdown used on field

[cylkee]

In the Indexes back-end page under the heading Included Fields, it would be helpful to be able to select the 'unformatted' version of a field where the Markdown Text Formatter has been applied, similar to that listed under Content > Included Elements in a Data Source. Otherwise, unparsed Markdown is output into the <excerpt>...</excerpt>