feat: ignore non-code lines after directive

[ycmjason]

This implementation leverage the fact that TypeScript's AST does not contain comment as nodes.

When we see @ts-migrating, we ignore the plugin errors in the next AST node's line.

This however mean that @ts-migrating will now not only skip subsequent comment lines, but also empty lines. For example:

// @ts-migrating

// bunch of words and empty lines

problematicLine();

This will still convert the problematicLine() to the old tsconfig.

I am not 100% sure if this is a good behaviour... @m-basov thoughts?

fixes #5