Resolve "load from rinex outside classes"

Closes #12 (closed)

include/gnss_utils/utils/utils.h

@@ -8,6 +8,7 @@
 
 #include "gnss_utils/internal/config.h"
 #include "gnss_utils/gnss_utils.h"
+#include "gnss_utils/observations.h"
 
 #define ARRAY_SIZE(arr) sizeof(arr) / sizeof(arr[0])
 #define ARRAY2D_NROWS(arr) sizeof(arr) / sizeof(arr[0])
@@ -165,6 +166,9 @@ bool equalArray3d(const T*   array_1,
   return true;
 }
 
+std::vector<Observations>
+loadObservationsFromRinex(const std::string& rnx_file, gtime_t t_start, gtime_t t_end, double dt, const char* opt);
+
 }  // namespace GnssUtils
 
 bool operator==(const gtime_t& time1, const gtime_t& time2);