feat(L04): add RV32I decoder and register file card

tests/task03_register_file_tb.sv

@@ -0,0 +1,21 @@
+module tb;
+    logic clk = 0, rst = 1, write_enable = 0;
+    logic [4:0] write_address = 0, read_address1 = 0, read_address2 = 0;
+    logic [31:0] write_data = 0, read_data1, read_data2;
+    string trace_file;
+    register_file dut (.*);
+    always #1 clk = ~clk;
+    initial begin
+        if ($value$plusargs("trace=%s", trace_file)) begin $dumpfile(trace_file); $dumpvars(0, tb); end
+        repeat (2) @(posedge clk); @(negedge clk); rst = 0;
+        write_enable = 1; write_address = 5; write_data = 32'h12345678;
+        @(posedge clk); #1; write_enable = 0;
+        read_address1 = 5; read_address2 = 0; #1;
+        if (read_data1 != 32'h12345678 || read_data2 != 0) $fatal(1, "FAIL task03 first read");
+        @(negedge clk); write_enable = 1; write_address = 0; write_data = 32'hffffffff;
+        @(posedge clk); #1; write_enable = 0; read_address1 = 0; read_address2 = 5; #1;
+        if (read_data1 != 0 || read_data2 != 32'h12345678) $fatal(1, "FAIL task03 x0 or dual read");
+        $display("PASS task03 x5=12345678 x0=00000000 dual_read=1");
+        $finish;
+    end
+endmodule