message: Add textsuperscript and textsubscript snippets
  Why? Mainly so I can reference them with keyboard shortcuts, also they're long to type. Not too sure about the current prefix though - any suggestions?
diff: "body": "\\textbf{${1:${TM_SELECTED_TEXT:text}}}",
  "description": "Use a bold font"
  },
  + "textsuperscript": {
  + "pre": "FSS",
  + "body": "\\testsuperscript{${1:${TM_SELECTED_TEXT:text}}}",
  + "description": "Make text a superscript"
  + },
  + "textsubscript": {
  + "pre": "FBS",
  + "body": "\\testsubscript{${1:${TM_SELECTED_TEXT:text}}}",
  + "description": "Make text a superscript"
  + },
  /* Math Formatting */
  "mathrm": {
  "prefix": "MRM",
  