Add initial wasm bindings for Instruction, SystemProgram and Transaction

(cherry picked from commit a35df1cb02)

sdk/program/src/wasm/instructions.rs

@@ -0,0 +1,28 @@
+//! The `Instructions` struct is a workaround for the lack of Vec<T> support in wasm-bindgen
+//! (ref: https://github.com/rustwasm/wasm-bindgen/issues/111)
+#![cfg(target_arch = "wasm32")]
+use {crate::instruction::Instruction, wasm_bindgen::prelude::*};
+
+#[wasm_bindgen]
+#[derive(Default)]
+pub struct Instructions {
+    instructions: Vec<Instruction>,
+}
+
+#[wasm_bindgen]
+impl Instructions {
+    #[wasm_bindgen(constructor)]
+    pub fn constructor() -> Instructions {
+        Instructions::default()
+    }
+
+    pub fn push(&mut self, instruction: Instruction) {
+        self.instructions.push(instruction);
+    }
+}
+
+impl From<Instructions> for Vec<Instruction> {
+    fn from(instructions: Instructions) -> Self {
+        instructions.instructions
+    }
+}