Update basaltPreview.lua

Copied from the Basalt wiki example

examples/basaltPreview.lua

@@ -1,7 +1,7 @@
 --Basalt configurated installer
 local filePath = "basalt.lua" --here you can change the file path default: basalt.lua
 if not(fs.exists(filePath))then
-    shell.run("pastebin run ESs1mg7P packed true "..filePath) -- this is an alternative to the wget command
+    shell.run("pastebin run ESs1mg7P packed true "..filePath:gsub(".lua", "")) -- this is an alternative to the wget command
 end
 local basalt = require(filePath:gsub(".lua", "")) -- here you can change the variablename in any variablename you want default: basalt