pr-9052.md

Fix self-closing blocks and blocks with src attribute format (#9052, #9055 by @fisker)

<!-- Input -->
<custom lang="markdown" src="./foo.md"></custom>
<custom lang="markdown" src="./foo.md" />
<custom lang="markdown" />

<!-- Prettier stable -->
<custom lang="markdown" src="./foo.md">

</custom>
<custom lang="markdown" src="./foo.md"

/>
<custom lang="markdown"

/>

<!-- Prettier master -->
<custom lang="markdown" src="./foo.md"></custom>
<custom lang="markdown" src="./foo.md" />
<custom lang="markdown" />