pragma extraction API

[OmarTawfik]

• Useful not only for end users, but can be used by both VS Code extension, and solidity-analyzer as well, as it will be able to handle/skip partial tokens correctly as the user is typing (for example pragma solidity ">0.<cursor>).
• The API should abstract over the various VST nodes/representations, and emit an analyzer type.
• Expose the same API through TypeScript.

let analysis = language.analyze_pragmas(root_node);

let result: bool = analysis.matches(version);