HeliBoard 2.0-beta1

Due to high activity in this repository and little available time from my side, the pile-up of pull requests and unanswered issues is going to increase further. Sorry, but I currently don't have enough time for everyone.

Changes since 2.0-alpha1:

• allow customizing functional key layouts
• slightly adjust symbols and more symbols layouts
• add options to auto-show/hide toolbar, by @codokie (#674)
• add toast notification when copying text, by @codokie (#752)
• separate language switch key behavior from enablement
• add comma key popups for number and phone layouts (#823)
• make long-press pinning in toolbar optional
• move toolbar settings to a separate section
• add tab key
• understand ctrl/alt/fn/meta key labels in layouts
• understand toolbar key labels in layouts
• add primary quotation marks for Norwegian bokmål, by @knutid
  (#806, #805)
• update Hebrew layout, by @codokie / @russianspy1234 (#735, #738)
• minor fixes and improvements