collapseWhitespace remove the space around the <output> tag

**how to reproduce:**

1. create example html file "input.html":
```html

Before output tag text 23 after output tag text.

Before b tag text 23 after b tag text.

2. run with collapseWhitespace parameter
```npx html-minifier --collapse-whitespace input.html -o output.html```

**html result "output.html":**
```html

Before output tag text23after output tag text.

Before b tag text 23 after b tag text.

**reason: the "output" is not a inline tag, but is often used as a inline (for javascript).**

Reproduce the issue with input.html and the npx html-minifier --collapse-whitespace command, comparing the output.html result for output and b tags. Start by tracing the collapseWhitespace handling of the output tag. Done means spaces around the output element are preserved as shown in the input while whitespace is still collapsed elsewhere.

Written by the indexing model from the issue text.