added contribution guide to instructions

hbvm/src/vm/mod.rs

@@ -137,6 +137,24 @@ impl<'a, PfHandler: HandlePageFault, const TIMER_QUOTIENT: usize>
             }
 
             // Big match
+            //
+            // Contribution guide:
+            // - Zero register shall never be overwitten. It's value has to always be 0.
+            //     - Prefer `Self::read_reg` and `Self::write_reg` functions
+            // - Extract parameters using `param!` macro
+            // - Prioritise speed over code size
+            //     - Memory is cheap, CPUs not that much
+            // - Do not heap allocate at any cost
+            //     - Yes, user-provided trap handler may allocate,
+            //       but that is not our »fault«.
+            // - Unsafe is kinda must, but be sure you have validated everything
+            //     - Your contributions have to pass sanitizers and Miri
+            // - Strictly follow the spec
+            //     - The spec does not specify how you perform actions, in what order,
+            //       just that the observable effects have to be performed in order and
+            //       correctly.
+            // - Yes, we assume you run 64 bit CPU. Else ?conradluget a better CPU
+            //   sorry 8 bit fans, HBVM won't run on your Speccy :(
             unsafe {
                 match *self.program.get_unchecked(self.pc) {
                     UN => {