Make `idris-info-mode` derived from `help-mode` and

[keram]

reuse existing functionality from help-mode for navigating through history and buffer handling.

Why: To reduce maintanance cost of maintaining own implementation and to improve user experience by relying on existing Emacs conventions. For example provided key bindings l r q by default to navigate through buffer history or close the buffer.

Breaking changes

• point does not move to the Idris info buffer when displaying Idris information (follows standard behaviour when invoking help commands like describe-function, describe-mode etc.)
• command idris-info-quit does not anymore kill the info buffer. Instead it burries the buffer for later use and remove it's window or restore it's previous buffer (behaviour of quit-window)

[jfdm]

Great work! Can we have the BREAKING changes documented in the CHANGELOG. It would be good if there was a high-level summary of the brilliant work you have been doing on the mode.