tridoraemu: fix crash on invalid vmem addresses

examples: removed 5cubes due to unclear licensing

add stuff to gitignore, licenses, README

import Vivado project

rtl/src/stack.v

@@ -0,0 +1,42 @@
+`timescale 1ns / 1ps
+//////////////////////////////////////////////////////////////////////////////////
+// Company: 
+// Engineer: 
+// 
+// Create Date: 17.01.2021 20:59:29
+// Design Name: 
+// Module Name: stack
+// Project Name: 
+// Target Devices: 
+// Tool Versions: 
+// Description: 
+// 
+// Dependencies: 
+// 
+// Revision:
+// Revision 0.01 - File Created
+// Additional Comments:
+// 
+//////////////////////////////////////////////////////////////////////////////////
+
+
+module stack
+    #(parameter ADDR_WIDTH=4, DATA_WIDTH=16)
+    (
+    input wire clk,
+    input wire [ADDR_WIDTH-1:0] rd_addr,
+    input wire [ADDR_WIDTH-1:0] wr_addr,
+    input wire wr_enable,
+    output wire [DATA_WIDTH-1:0] rd_data,
+    input wire [DATA_WIDTH-1:0] wr_data
+    );
+    
+    reg [DATA_WIDTH-1:0] stack[0:2**ADDR_WIDTH-1];
+    
+    always @(posedge clk)
+    begin
+        if(wr_enable) stack[wr_addr] <= wr_data;
+    end
+    
+    assign rd_data = stack[rd_addr];
+endmodule