docs: moving code examples

Code now resides in `docs/source/code_examples`.
`CHAPTER_Prog` -> `stubnets`
`APPNOTE_011_Design_Investigation` -> `selections` and `show`
`resources/PRESENTATION_Intro` -> `intro`
`resources/PRESENTATION_ExSyn` -> `synth_flow`
`resources/PRESENTATION_ExAdv` -> `techmap`,  `macc`, and `selections`
`resources/PRESENTATION_ExOth` -> `scrambler` and `axis`

Note that generated images are not yet configured to build from the new code locations.

docs/source/code_examples/synth_flow/memory_02.v

@@ -0,0 +1,27 @@
+module test(
+    input             WR1_CLK,  WR2_CLK,
+    input             WR1_WEN,  WR2_WEN,
+    input      [7:0]  WR1_ADDR, WR2_ADDR,
+    input      [7:0]  WR1_DATA, WR2_DATA,
+    input             RD1_CLK,  RD2_CLK,
+    input      [7:0]  RD1_ADDR, RD2_ADDR,
+    output reg [7:0]  RD1_DATA, RD2_DATA
+);
+
+reg [7:0] memory [0:255];
+
+always @(posedge WR1_CLK)
+    if (WR1_WEN)
+        memory[WR1_ADDR] <= WR1_DATA;
+
+always @(posedge WR2_CLK)
+    if (WR2_WEN)
+        memory[WR2_ADDR] <= WR2_DATA;
+
+always @(posedge RD1_CLK)
+    RD1_DATA <= memory[RD1_ADDR];
+
+always @(posedge RD2_CLK)
+    RD2_DATA <= memory[RD2_ADDR];
+
+endmodule