add compatBird213 flag

[skoef]

To solve issue #21 , the compatbird213 configuration flag was introduced. This will remove the return type from the functions.
Template rendering was overhauled a bit as well.

[sonarqubecloud]

Quality Gate failed

Failed conditions
8 Security Hotspots
24.4% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud

[tommysitehost]

cat /etc/birdwatcher.conf
compatbird213 = true
[services]
  [services."foo"]
  command = "echo test > /tmp/test"
  prefixes = ["192.168.0.0/24", "fc00::/7"]

This config generates

# DO NOT EDIT MANUALLY
function match_route()
{
	return net ~ [
		192.168.0.0/24,
		fc00::/7
	];
}

Without compatbird213 flag, it generates

# DO NOT EDIT MANUALLY
function match_route() -> bool
{
	return net ~ [
		192.168.0.0/24,
		fc00::/7
	];
}

appears to be working for me. I only tested config generation.

[skoef]

Thanks for testing @tommysitehost, I'll create a new release!