Mainly small install script improvements - Consistent usage of `$LUANHOME`, removed reliance on current directory. - Made Luan build and install fine (on Linux) without requiring launching it via sudo. Only asks to elevate privileges if installation failed. - Minor spelling mistake fix.

local Luan = require "luan:Luan.luan"
local error = Luan.error
local Web_search = require "luan:lucene/Web_search.luan"
local Db = require "site:/lib/Db.luan"

return Web_search.of(Db)