public boolean isJson() {
        return is(JSON) || subtype().endsWith("+json");
    }
Returns {@code true} when the subtype is {@link MediaType#JSON} or ends with {@code +json}.
Otherwise {@code false}.

<pre>{@code
JSON.isJson() // true
JSON_UTF_8.isJson() // true
PLAIN_TEXT_UTF_8.isJson() // false
MediaType.parse("application/graphql+json").isJson() // true
}</pre>
core/src/main/java/com/linecorp/armeria/common/MediaType.java