fix pressing TAB in the editor

[wkiril]

Pressing TAB key should insert TAB symbol in the editor. closes #132

[xy2z]

Thanks, but after testing I found a few issues

• If shift+tab is pressed, it should not insert a tab.
• When I refresh the page, the tab is gone in the editor. (it is saved in the database, so it's on rendering)
• When pressing tab in a list it should not insert a tab, since tiptap already has a event for this - i'm not sure how this can be detected.

[wkiril]

alright, I'll try to address those issues, thanks for the feedback