feat: add reset button to entry details

[Hamedamz]

It adds a reset button (LinkButton) before save button in the entry details view.
Fixes #91

[CLAassistant]

All committers have signed the CLA.

[hpoul]

Hi, thanks for your PR.
unfortunately i don't think this will work correctly. This will only reset the values in the form fields to those in the kdbx models. But those are changed for example for passwords on every blur.. or when adding/removing fields..
I have to admit this is not really a clean implementation to begin with, because some state is only written "onSave" while others immediately triggered by other actions (changing entry structure, attaching files, etc.).

I think it would be easier to have a file-level "reset" where i can revert all changes in a file.. basically a close and reopen of the whole file.. 🤔️ (maybe more of a 'reset' button in the app bar next to the 'save' icon when the file is dirty)
The file shouldn't be "dirty" after changes have been reverted..