Make js.webassembly option stable and allowed in sandboxed mode.

(cherry picked from commit 2a26d91)

Author: woess

graal-js/src/com.oracle.truffle.js/src/com/oracle/truffle/js/runtime/JSContextOptions.java

@@ -540,7 +540,7 @@ public Map<String, String> apply(String value) {
     @CompilationFinal private boolean useUTCForLegacyDates;
 
     public static final String WEBASSEMBLY_NAME = JS_OPTION_PREFIX + "webassembly";
-    @Option(name = WEBASSEMBLY_NAME, category = OptionCategory.EXPERT, help = "Enable WebAssembly JavaScript API.") //
+    @Option(name = WEBASSEMBLY_NAME, category = OptionCategory.USER, stability = OptionStability.STABLE, help = "Enable WebAssembly JavaScript API.") //
     public static final OptionKey<Boolean> WEBASSEMBLY = new OptionKey<>(false);
     @CompilationFinal private boolean webAssembly;