ASTConveter javadoc pending tests for the snippet tag

[subyssurendran666]

Snippet tag was introduced in java18 and some of the scenarios covered in the ASTConverterJavadocTest_18. The remaining scenarios are following.

1. Empty Body

---

{@snippet :
}

2. Single Element

---

{@snippet :
int a = 10; 
}

3. Multi-line plain code

---

{@snippet :
  int a = 1;
  int b = 2;
}

4. Blank line inside body

---

{@snippet :

int a = 1;

int b = 2;
}

5. Multiple attribute

---

{@snippet id="x1" lang=java region="main" :
  int a;
}

6. Single quote attributes

---

{@snippet id='demo' lang='java' :
  int a;
}

7. Nested blocks

---

{@snippet :
  if (a) {
     while (b) {
        foo();
     }
  }
}

8. {@code} inside snippet (here code tag will treat as plain text)

---

{@snippet :
 {@code int a = 0;}
}

9. Replace tag

---

{@snippet :
System.out.println("abc"); // @replace substring="abc" replacement="xyz"
}

10. Link tag

---

{@snippet : 
  System.out.println("abc"); //@link substring="System" target="System"
 }

[RagiGeorge]

@subyssurendran666
Can I please work on it