feat(compiler): Add support for targeting WebAssembly.

The working principle is similar as before with x86, but instead of outputting .asm, it outputs .wat. This can be compiled into .wasm by using the wat2wasm assembler.

templates/amd64-386/flowcontrol.asm

@@ -0,0 +1,23 @@
+{{- if .HasOp "speed" -}}
+;-------------------------------------------------------------------------------
+;   SPEED opcode: modulate the speed (bpm) of the song based on ST0
+;-------------------------------------------------------------------------------
+;   Mono: adds or subtracts the ticks, a value of 0.5 is neutral & will7
+;   result in no speed change.
+;   There is no STEREO version.
+;-------------------------------------------------------------------------------
+{{.Func "su_op_speed" "Opcode"}}
+{{- .Float 2.206896551724138 | .Prepare | indent 4}}
+    fmul    dword [{{.Float 2.206896551724138 | .Use}}]         ; (2*s-1)*64/24, let's call this p from now on
+    {{.Call "su_power"}}
+    fld1                                 ; 1 2^p
+    fsubp   st1, st0                     ; 2^p-1, the player is advancing 1 tick by its own
+    fadd    dword [{{.WRK}}] ; t+2^p-1, t is the remainder from previous rounds as ticks have to be rounded to 1
+    push    {{.AX}}
+    fist    dword [{{.SP}}]                  ; Main stack: k=int(t+2^p-1)
+    fisub   dword [{{.SP}}]                  ; t+2^p-1-k, the remainder
+    pop     {{.AX}}
+    add     dword [{{.Stack "Sample"}}], eax          ; add the whole ticks to row tick count
+    fstp    dword [{{.WRK}}] ; save the remainder for future
+    ret
+{{end}}