Add blinky_ext example to tinyfpga_ax to test external clock.

examples/tinyfpga_ax/blinky_ext.lpf

diff --git a/examples/tinyfpga_ax/blinky_ext.lpf b/examples/tinyfpga_ax/blinky_ext.lpf
new file mode 100644
index 0000000..6bc4413
--- /dev/null
+++ b/examples/tinyfpga_ax/blinky_ext.lpf
@@ -0,0 +1,4 @@
+BLOCK RESETPATHS ;
+BLOCK ASYNCPATHS ;
+LOCATE COMP "pin1" SITE "13" ;
+LOCATE COMP "clk" SITE "21" ;

examples/tinyfpga_ax/blinky_ext.v

diff --git a/examples/tinyfpga_ax/blinky_ext.v b/examples/tinyfpga_ax/blinky_ext.v
new file mode 100644
index 0000000..b05e409
--- /dev/null
+++ b/examples/tinyfpga_ax/blinky_ext.v
@@ -0,0 +1,17 @@
+// Modified from:
+// https://github.com/tinyfpga/TinyFPGA-A-Series/tree/master/template_a2
+
+module TinyFPGA_A2 (
+  inout pin1,
+  input clk
+);
+
+  reg [23:0] led_timer;
+
+  always @(posedge clk) begin
+    led_timer <= led_timer + 1;
+  end
+
+  // left side of board
+  assign pin1 = led_timer[23];
+endmodule