zio.http.internal.OutputEncoder does not correctly encode '&' char

[kadriaen-bb]

Describe the bug
zio.http.internal.OutputEncoder does not correctly encode '&' char.
It encodes it as &amp instead of & (missing ';' char).
This causes url's in href attributes to get garbled.

To Reproduce
render a zio template containing:

a(
   href := "http://www.myservice.com?param1=v1&param2=v2",
   s"Click here"
)

this renders the href like:
href = "http://www.myservice.com?param1=v1&ampparam2=v2"
(missing ';' at the end of '&amp')

Expected behaviour
html code showing the href rendered like:
href = "http://www.myservice.com?param1=v1&param2=v2"

Screenshots

Desktop (please complete the following information):

• OS: OSX
• Browser: any
• Version 3.0.1

Smartphone (please complete the following information):
Any

Additional context
None