feat: add wasmtime

__wasm/wasmtime/hello_world.wat

@@ -0,0 +1,27 @@
+(module
+    ;; Import the required fd_write WASI function which will write the given io vectors to stdout
+    ;; The function signature for fd_write is:
+    ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written
+    (import "wasi_unstable" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))
+
+    (memory 1)
+    (export "memory" (memory 0))
+
+    ;; Write 'hello world\n' to memory at an offset of 8 bytes
+    ;; Note the trailing newline which is required for the text to appear
+    (data (i32.const 8) "hello world\n")
+
+    (func $main (export "_start")
+        ;; Creating a new io vector within linear memory
+        (i32.store (i32.const 0) (i32.const 8))  ;; iov.iov_base - This is a pointer to the start of the 'hello world\n' string
+        (i32.store (i32.const 4) (i32.const 12))  ;; iov.iov_len - The length of the 'hello world\n' string
+
+        (call $fd_write
+            (i32.const 1) ;; file_descriptor - 1 for stdout
+            (i32.const 0) ;; *iovs - The pointer to the iov array, which is stored at memory location 0
+            (i32.const 1) ;; iovs_len - We're printing 1 string stored in an iov - so one.
+            (i32.const 20) ;; nwritten - A place in memory to store the number of bytes written
+        )
+        drop ;; Discard the number of bytes written from the top of the stack
+    )
+)