Merge branch 'hotfix/error-startup' into develop

* hotfix/error-startup:
  fixed startup error #33
fixed none recent file exception #35
update stacks
impletement Save as action
impletement Save as action #36
add auto .md ext
add Audo .md ext #37
enhance editor s change event logic
set default background color in viewer
change logic based event
markdown file open issues
enhancement save logic
add comment for TODO
implements & fixes #22, #41

* feature/openning-file:
  add comment for TODO
  enhancement save logic
  markdown file open issues
  change logic based event
  set default background color in viewer
  enhance editor s change event logic
fixed associated error #41
fixed #44
Merge branch 'feature/error-shift-link-click' into develop

* feature/error-shift-link-click:
  fixed #44
fixed #50, shake cursor position error
Merge branch 'feature/shake-cursor-position' into develop

* feature/shake-cursor-position:
  fixed #50, shake cursor position error
fixed #31 image path at refresh time