luaHow to check if file exists

We'll use io.open to try to open file and return true or false based on this attempt:

local file_exists = io.open('/tmp/test.txt', "r") ~= nilctrl + cyoutubegithub

`file_exists` will contain `true` if file exists, otherwise `false`	`io.open` opens file handler
`/tmp/test.txt` file to check existence of	`~= nil` compare value with `nil` (returned if there's no file)

local file_exists = io.open('/tmp/test.txt', "r") ~= nil
print(file_exists)

local file_exists = io.open('unknow.txt', "r") ~= nil
print(file_exists)

true
false