build: More repo cleanup, move libimhex and external libs to /lib folder

lib/libimhex/include/hex/pattern_language/validator.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <hex.hpp>
+
+#include <string>
+#include <vector>
+
+namespace hex::pl {
+
+    class ASTNode;
+
+    class Validator {
+    public:
+        Validator();
+
+        bool validate(const std::vector<ASTNode*>& ast);
+
+        const std::pair<u32, std::string>& getError() { return this->m_error; }
+
+    private:
+        std::pair<u32, std::string> m_error;
+
+        using ValidatorError = std::pair<u32, std::string>;
+
+        [[noreturn]] void throwValidateError(std::string_view error, u32 lineNumber) const {
+            throw ValidatorError(lineNumber, error);
+        }
+
+    };
+
+}