bug#68297: [PATCH] Support indented continuation lines in lua-ts-mode

[john muhl]

Add rules for indenting multi-line variables and if/elseif
statements, e.g.:

  local very_long_variable_name =
      "ABC"..
      "XYZ"
  local v = 123 *
      456 +
      789

  if a
      and b
      or c then
      print(1)
  elseif b
      and c
      or a then
      print(0)
  end

The lua-ts-indent-continuation-lines option can be set to nil to
keep if statements flush left:

  if a
  and b
  or c then
      print(1)
  elseif b
  and c
  or a then
      print(0)
  end

The option controlling this behavior in the EmmyLua code
formatter does not affect multi-line variables so neither does
lua-ts-indent-continuation-lines.