nSLOC does not properly count abstract/interface function lines

[IllIllI000]

solidity-metrics/src/metrics/metrics.js

Lines 989 to 994 in 1bc713a

	// get normalized sloc (function heads normalized)
	const normalized = content.replace(
	/function\s*\S+\s*\([^{]*/g,
	'function ',
	content
	);

The regex looks for a beginning curly brace, which may not exist in an interface or an abstract contract's function declaration. This can be addressed with the following change, which looks for a semicolon in addition to the opening curly brace:

-       /function\s*\S+\s*\([^{]*/g,
+       /function\s*\S+\s*\([^{;]*/g,