add copy/paste support to the frequency selector

core/src/utils/hrfreq.h

@@ -0,0 +1,19 @@
+#pragma once
+#include <string>
+
+namespace hrfreq {
+    /**
+     * Convert a frequency to a human-readable string.
+     * @param freq Frequency in Hz.
+     * @return Human-readable representation of the frequency.
+    */
+    std::string toString(double freq);
+
+    /**
+     * Convert a human-readable representation of a frequency to a frequency value.
+     * @param str String containing the human-readable frequency.
+     * @param freq Value to write the decoded frequency to.
+     * @return True on success, false otherwise.
+    */
+    bool fromString(const std::string& str, double& freq);
+}