correct various names in this and other pre-freewheeling forks

Dependencies

• [2] N2NUGNN4 include a brief reference enabling many useful apps
• [3] H5UZI3YN editor documentation
• [4] H7WUFI5V fix method name in documentation
• [5] A27WWJ6H document a few more keyboard primitives
• [6] 7IDHIAYI rename modifier_down to key_down
• [7] MXXCTVXW document facilities for buttons on screen

Change contents

• replacement in reference.md at line 39
  [2.1773]→[2.1773:1788](∅→∅)
  − `on.resize`.
  [2.1773]

  [2.1788]
  + `App.resize`.
• replacement in reference.md at line 54
  [2.2384]→[2.2384:2613](∅→∅)
  − * `App.update(dt)` -- called after every call to `on.draw`. Make changes to

  − your app's variables here rather than in `on.draw`. Provides in `dt` the

  − time since the previous call to `on.update`, which can be useful for things
  [2.2384]

  [2.2613]
  + * `App.update(dt)` -- called after every call to `App.draw`. Make changes to

  + your app's variables here rather than in `App.draw`. Provides in `dt` the

  + time since the previous call to `App.update`, which can be useful for things
• replacement in reference.md at line 70
  [2.3298]→[2.3298:3365](∅→∅)
  − button. Provides the same arguments as `on.mouse_press()` above.
  [2.3298]

  [2.3365]
  + button. Provides the same arguments as `App.mousepressed()` above.
• replacement in reference.md at line 91
  [2.4474]→[2.4474:4520](∅→∅)
  − together will call `on.textinput` with `A`.
  [2.4474]

  [2.4520]
  + together will call `App.textinput` with `A`.
• replacement in reference.md at line 314
  [2.9114]→[2.9114:9190](∅→∅)
  − `mouse_button` is pressed. See `on.mouse_press` for `mouse_button` codes.
  [2.9114]

  [2.9190]
  + `mouse_button` is pressed. See `App.mousepressed` for `mouse_button` codes.