fix: Suggested Rollup config corrupts output html

[timfish]

Pull Request

📖 Description

I found that the suggested Rollup config results in corrupted html:

In the output bundle you can see the missing space:

I tied these regexes and they fix the issue: https://github.com/microsoft/fast/blob/50dba9c58b1bc6ac0c8b948f68dd0cfb6485460b/build/transform-fragments.js

• [ ] I have included a change request file using $ yarn change
• [ ] I have added tests for my changes.
• [x] I have tested my changes.
• [x] I have updated the project documentation to reflect my changes.
• [x] I have read the CONTRIBUTING documentation and followed the standards for this project.

[timfish]

There are probably still some improvements to be had with the css regex since the output still has some unnessary spaces:

[timfish]

The css regex in transform-fragments.js actually needs a minor addition. It doesn't strip leading whitespace and needs an additional ^\s+.

https://github.com/microsoft/fast/blob/50dba9c58b1bc6ac0c8b948f68dd0cfb6485460b/build/transform-fragments.js#L31

So it would become:

/(?:\s*\/\*(?:[\s\S])+?\*\/\s*)|(?:;)\s+(?=\})|\s+(?=\{)|(?<=:)\s+|\s*([{};,])\s*|^\s+/g

Shall I create a PR for that first?