[sitecore-jss-proxy] Prevent passing 'qs' as 'undefined' in rewriteRequestPath

[jpspringall]

When solely using qsParams undefined was included in the querystring

Description

In the function isUrlIgnored,
When solely using qsParams undefined would be appended to the resulting queystring
e.g: '/sitecore/layoutsvc/render/jss?item=%2Fabout&sc_apikey={GUID}&undefined&sc_site=mysite';

I note it has also updated the formatting on the file.
I note there is a .prettierrc file, as I user prettier, I'm assuming that this formatting changes are valid

Motivation

Ensure resultant querystring matches convention

How Has This Been Tested?

New unit test added

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update (non-breaking change; modified files are limited to the /docs directory)

Checklist:

• I have read the Contributing guide.
• My code follows the code style of this project.
• My code/comments/docs fully adhere to the Code of Conduct.
• My change is a code change and it requires an update to the documentation.
• My change is a documentation change and it requires an update to the navigation.