manual test for adjusting line width

Dependencies

• [2] XF2BJIPT .
• [*] BJ5X5O4A let's prevent the text cursor from ever getting on a drawing

Change contents

• edit in Manual_tests.md at line 19
  [2.179]
  +

  + * line-width button

  + * Create a file containing a single line with a reasonable number of

  + characters. Move the cursor towards the end of the line. Click on

  + line-width icon in the top margin, slide it left and right. Watch the line

  + of characters wrap and unwrap in response. Text should not be selected.