Redactor 2 - Can a text alignment button be added? Left, Center, Right -- Can the text alignment button be added to Redactor 2, and if so, how?
You can use the formattingAdd config setting to add custom formatting to the "Format" dropdown.

formattingAdd: {
  "align-left": {
    "title": "Align left",
    "args": ["p","class","align-left"],
  },
  "align-right": {
    "title": "Align right",
    "args": ["p","class","align-right"],
  },
  "align-center": {
    "title": "Align center",
    "args": ["p","class","align-center"],
  },
  "align-justify": {
    "title": "Justify",
    "args": ["p","class","align-justify"],
  },
},


If you want to have a separate dropdown or individual buttons in the toolbar for this functionality, have a look at my plugin Redactor Inline Styles.