'o' and 'a' from Vim

src/main.cpp

@@ -226,6 +226,24 @@ int main(int argc, char** argv) {
                         lines = undoHistory[undos].lines;
                         pos = undoHistory[undos].pos;
                         break;
+                    case 'a':
+                        currMode = mode::INSERT;
+                        if (!(pos.x + 1 > lines[pos.y].size())) {
+                            pos.x ++;
+                        } 
+                        break;
+                    case 'o':
+                        currMode = mode::INSERT;
+                    {
+                        size_t line_idx = pos.y - 1;
+                        if (line_idx < lines.size()) {
+                            lines.insert(lines.begin() + line_idx + 1, "");
+                            pos.y++;
+                            pos.x = 0;
+                            if (!fileChanged) fileChanged = true;
+                        }
+                    }
+                        break;
                     case 'h':
                     case KEY_LEFT:
                         if (pos.x > 0) {