chore: add missing definitions to the files. remove static qualifier from the headers. add help text to the actions.

src/source/conventions/base_convention.cpp

@@ -2,12 +2,12 @@
 #include <algorithm>
 
 namespace argument_parser::conventions::helpers {
-	static std::string to_lower(std::string s) {
+	std::string to_lower(std::string s) {
 		std::transform(s.begin(), s.end(), s.begin(), [](unsigned char c) { return std::tolower(c); });
 		return s;
 	}
 
-	static std::string to_upper(std::string s) {
+	std::string to_upper(std::string s) {
 		std::transform(s.begin(), s.end(), s.begin(), [](unsigned char c) { return std::toupper(c); });
 		return s;
 	}