Feature: More coherent user errors

[FredHappyface]

Feature

• I have read the comment above and have completed each step
• I have filled in each heading below

Is your feature request related to a problem? Please describe

Error messages are pretty poor at the moment in the application. This issue is to track proposed changes at enhancing feedback to the end-user. This may help with some issues like #37. For example, one cause of the above issue may be that the user is meeting sticker import limits. At present the app does nothing to inform them of this

Describe the solution you'd like

Enhanced feedback through toast notifications to inform the user of

• Sticker Pack size limits (present to reduce the number of crashes from giant sticker packs)
• Total sticker limits (present to reduce number of crashes from selecting a root directory by accident)
• Other sticker import issues (where the number of stickers differs from the number of files)
• Other warnings/ errors not yet decided

Describe alternatives you've considered

Initial ideas:

Can probably create a class for this that triggers a toast notification and keeps an internal 'exit code' type state. Then can filter output. Eg.

• Toaster.toast() to generate toast regardless.
• Toaster.toasterror() to generate an error and set the error flag.
• Toaster.toastiferror() to generate erro is error flag is set
• Toaster.toastifsuccess() to generate success message (only if the error flag is unset)

Additional context