There are many options to change the font size in the Visual studio code(version:1.36.1), Editor
Go To: File > Preferences > Settings > select User tab > Text Editor > Font > Font Size
Font Size: Change font size in pixels as per your requirement
Press Ctrl + P
Search: settings.json, Open file and add this line in settings.json file:
{
"editor.fontSize": 20
}
Note: Save file after changes
Press Ctrl + Shift + P
Search: Editor Font Zoom In
Search: Editor Font Zoom Out