adding Zig examples

EXAMPLES_Zig/jetgpio_round_trip.zig

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+// Usage example of the JETGPIO library
+// Compile with: zig build-exe jetgpio_round_trip.zig -ljetgpio -lc
+// Execute with: sudo ./jetgpio_round_trip
+
+const std = @import("std");
+const jetgpio = @cImport({
+    @cInclude("jetgpio.h");
+});
+
+pub fn main() !void {
+    const init = jetgpio.gpioInitialise();
+
+    if (init < 0) {
+        std.debug.print("Error initiating jetgpio\n", .{});
+    }
+    // Setting up pin 38 as output
+    const set1 = jetgpio.gpioSetMode(38, jetgpio.JET_OUTPUT);
+    if (set1 < 0) {
+        std.debug.print("Error setting pin 38\n", .{});
+    }
+
+    // Setting up pin 40 as input
+    const set2 = jetgpio.gpioSetMode(40, jetgpio.JET_INPUT);
+    if (set2 < 0) {
+        std.debug.print("Error setting pin 40\n", .{});
+    }
+
+    // Measuring time now
+    const start = try std.time.Instant.now();
+
+    // Writing 1 to pin 38
+    _ = jetgpio.gpioWrite(38, 1);
+
+    while (jetgpio.gpioRead(40) == 0) {}
+
+    // Measuring time after the loop
+    const end = try std.time.Instant.now();
+
+    // Calculating time difference for round trip e.g. time invested in activating the output + the time it takes for the input to detect the level change
+    const elapsed = end.since(start);
+    std.debug.print("Elapsed time = {} nanoseconds\n", .{elapsed});
+
+    // Writing 0 to pin 38
+    _ = jetgpio.gpioWrite(38, 1);
+
+    jetgpio.gpioTerminate();
+}