Add C++ tool for conversion csv logs to ulog

tools/csv_to_ulog/README.md

@@ -0,0 +1,20 @@
+# csv_to_ulog
+
+Tool for converting CSV flight logs to ULog format so they can be analyzed using [FlightPlot](https://github.com/PX4/FlightPlot) software.
+
+To build, go to the `<flix>/tools/csv_to_ulog` directory and run:
+
+```bash
+mkdir build
+cd build
+cmake ..
+make
+```
+
+Convert a CSV file to ULog:
+
+```bash
+./csv_to_ulog log_file.csv
+```
+
+ULog file will be saved in the same directory.