get_preview

[get_preview](https://www.dropbox.com/developers/documentation/http/documentation#files-get_preview) scope: `files.content.read` Get a preview for a file. Currently, PDF previews are generated for files with the following extensions: .ai, .doc, .docm, .docx, .eps, .gdoc, .gslides, .odp, .odt, .pps, .ppsm, .ppsx, .ppt, .pptm, .pptx, .rtf. HTML previews are generated for files with the following extensions: .csv, .ods, .xls, .xlsm, .gsheet, .xlsx. Other formats will return an unsupported exte...