Improve generated type defininitions for ASModule (#1510)

Author: MaxGraey

Diff for: src/definitions.ts

@@ -600,24 +600,24 @@ export class TSDBuilder extends ExportsWalker {
     sb.push("  type i8 = number;\n");
     sb.push("  type i16 = number;\n");
     sb.push("  type i32 = number;\n");
-    sb.push("  type i64 = BigInt;\n");
+    sb.push("  type i64 = bigint;\n");
     if (isWasm64) {
-      sb.push("  type isize = BigInt;\n");
+      sb.push("  type isize = bigint;\n");
     } else {
       sb.push("  type isize = number;\n");
     }
     sb.push("  type u8 = number;\n");
     sb.push("  type u16 = number;\n");
     sb.push("  type u32 = number;\n");
-    sb.push("  type u64 = BigInt;\n");
+    sb.push("  type u64 = bigint;\n");
     if (isWasm64) {
-      sb.push("  type usize = BigInt;\n");
+      sb.push("  type usize = bigint;\n");
     } else {
       sb.push("  type usize = number;\n");
     }
     sb.push("  type f32 = number;\n");
     sb.push("  type f64 = number;\n");
-    sb.push("  type bool = any;\n");
+    sb.push("  type bool = boolean | number;\n");
     ++this.indentLevel;
     this.walk();
     --this.indentLevel;