Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/vanetza/gnss/nmea.hpp

@@ -0,0 +1,58 @@
+#ifndef NMEA_HPP_EJIHQ65L
+#define NMEA_HPP_EJIHQ65L
+
+#include <vanetza/units/angle.hpp>
+#include <vanetza/units/velocity.hpp>
+#include <vanetza/units/length.hpp>
+#include <boost/date_time/posix_time/posix_time_types.hpp>
+#include <cstdint>
+#include <string>
+
+namespace vanetza
+{
+
+// forward declaration
+struct Wgs84Point;
+
+namespace nmea
+{
+typedef boost::posix_time::ptime time;
+
+enum class Quality
+{
+    Unavailable = 0,
+    GPS = 1,
+    DGPS = 2,
+    PPS = 3,
+    RTK = 4,
+    Float_RTK = 5,
+    Estimated = 6,
+    Manual = 7,
+    Simulation = 8
+};
+
+enum class RMCStatus : char
+{
+    Warning = 'V',
+    Valid = 'A'
+};
+
+enum class FAAMode : char
+{
+    Autonomous = 'A',
+    Differential = 'D',
+    Estimated = 'E',
+    Manual = 'M',
+    Simulated = 'S',
+    Invalid = 'N'
+};
+
+std::string gprmc(const time&, const Wgs84Point&, units::NauticalVelocity ground, units::TrueNorth heading);
+std::string gpgga(const time&, const Wgs84Point&, Quality, units::Length hdop);
+uint8_t checksum(std::string::const_iterator, std::string::const_iterator);
+
+} // namespace nmea
+} // namespace vanetza
+
+#endif /* NMEA_HPP_EJIHQ65L */
+