Fix NotSupportedException with ${aspnet-request-posted-body}

[304NotModified]

• update example

fixes #429

[codecov-io]

Codecov Report

Merging #431 into dev will decrease coverage by <1%.
The diff coverage is n/a.

@@         Coverage Diff         @@
##           dev   #431    +/-   ##
===================================
- Coverage   62%    62%   -<1%     
===================================
  Files       35     35            
  Lines      528    524     -4     
  Branches   122    121     -1     
===================================
- Hits       329    325     -4     
+ Misses     162    158     -4     
- Partials    37     41     +4

Impacted Files	Coverage Δ
.../Shared/LayoutRenderers/AspNetRequestPostedBody.cs	47% <ø> (+3%)	⬆️
...d/LayoutRenderers/AspNetItemValueLayoutRenderer.cs	86% <0%> (-7%)	⬇️
...enderers/AspNetRequestQueryStringLayoutRenderer.cs	82% <0%> (-5%)	⬇️
...youtRenderers/AspNetRequestCookieLayoutRenderer.cs	88% <0%> (-4%)	⬇️
...outRenderers/AspNetLayoutMultiValueRendererBase.cs	88% <0%> (-1%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ed84a18...ce55437. Read the comment docs.