message: Clarify some commands are math commands.
diff: "mathrm": {
  "prefix": "MRM",
  "body": "\\mathrm{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "roman font"
  + "description": "math roman font"
  },
  "mathbf": {
  "prefix": "MBF",
  "body": "\\mathbf{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "bold font"
  + "description": "math bold font"
  },
  "mathbb": {
  "prefix": "MBB",
  "body": "\\mathbb{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "blackboard bold font"
  + "description": "math blackboard bold font"
  },
  "mathcal": {
  "prefix": "MCA",
  "body": "\\mathcal{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "caligraphic font"
  + "description": "math caligraphic font"
  },
  "mathit": {
  "prefix": "MIT",
  "body": "\\mathit{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "italic text font (good for variable names)"
  + "description": "math italic font"
  },
  "mathtt": {
  "prefix": "MTT",
  "body": "\\mathtt{${1:${TM_SELECTED_TEXT:text}}}",
  - "description": "typewriter font"
  + "description": "math typewriter font"
  },
  "alpha": {
  "prefix": "@a",
  