linter: Add shebang so it can be run directly

[spaze]

• BC break? no
• new feature? yes but tiny

Hi, I was happy to see linter added ❤ but when I ran it like this:

$ vendor/latte/latte/bin/latte-lint

I got

vendor/latte/latte/bin/latte-lint: line 1: ?php: No such file or directory

because I didn't run it like (omitted php because I didn't expect it needs to be added)

$ php vendor/latte/latte/bin/latte-lint

This PR adds a shebang line to latte-lint so it can be executed directly without php in the command line.
Also the executable flag is added to the script.

This is in line with other similar tools (like for example tester).

Thanks!

[dg]

Thanks