Language server cannot correctly report diagnostics for sources containing multibyte characters

[kyoh86]

Bug description

If a source contains multi-byte characters, Prisma Language Server cannot report diagnostics with correct position.

e.g.

// 📅📅📅📅📅
enum Day {
  Monday
  Tuesday
  Wednesday
  Thursday,
  Friday
  Saturday
  Sunday
}

It must be reported that a problem is in the line Thursday, that is not an enum value definition.
But the problem is reported in a position of Friday.

While you put a charater 📅 more, the reported position also shift.

How to reproduce

• Write prisma schema
• Make it invalid
• Put multi-byte character before the invalid line.

Expected behavior

The problem is reported in correct position.

Prisma information

// 📅📅📅📅📅
enum Day {
  Monday
  Tuesday
  Wednesday
  Thursday,
  Friday
  Saturday
  Sunday
}

Environment & setup

• OS: Arch Linux
• Editor: Neovim
• Editor version: v0.10.0-dev-344906a