Improve Selection Issue

[schrieveslaach]

@blinry reported in ethersync/ethersync#257

• When selecting something "backwards" in Neovim (so that the "end" of the selection is in front of the "start"), the selection is not displayed in Intellij. (We decided to allow those selections, so that editors could mark the "active end" of the selection.)
• When selecting something in Intellij, Neovim seems to receive only the current cursor position, not the full selection.
• When receiving a cursor position on an empty line, the Intellij plugin doesn't render it.