Improve sway/language

include/util/string.hpp

@@ -0,0 +1,15 @@
+#include <string>
+
+const std::string WHITESPACE = " \n\r\t\f\v";
+
+std::string ltrim(const std::string s) {
+  size_t begin = s.find_first_not_of(WHITESPACE);
+  return (begin == std::string::npos) ? "" : s.substr(begin);
+}
+
+std::string rtrim(const std::string s) {
+  size_t end = s.find_last_not_of(WHITESPACE);
+  return (end == std::string::npos) ? "" : s.substr(0, end + 1);
+}
+
+std::string trim(const std::string& s) { return rtrim(ltrim(s)); }