fix(markdown): stably print lists in front of whitespace-only trailing newline

[ikatyang]

Fixes #5021

Prettier pr-5024
Playground link

--parser babylon

Input:

if (true) {
  md`
text1
- 123
  - 456

text2
- 123
  - 456

text3
- 123
  - 456
`;
}

Output:

if (true) {
  md`
text1

- 123
  - 456

text2

- 123
  - 456

text3

- 123
  - 456
  `;
}

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in the docs/ directory)
• I’ve read the contributing guidelines.