Update README.md

[stnc]

added pongo2echo template middleware

[codecov]

Codecov Report

Merging #1646 into master will decrease coverage by 1.50%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1646      +/-   ##
==========================================
- Coverage   85.28%   83.78%   -1.51%     
==========================================
  Files          28       28              
  Lines        2216     1906     -310     
==========================================
- Hits         1890     1597     -293     
+ Misses        212      195      -17     
  Partials      114      114              

Impacted Files	Coverage Δ
middleware/method_override.go	80.95% <0.00%> (-3.67%)	⬇️
context.go	86.38% <0.00%> (-3.34%)	⬇️
middleware/redirect.go	85.00% <0.00%> (-3.24%)	⬇️
middleware/proxy.go	63.21% <0.00%> (-3.12%)	⬇️
middleware/basic_auth.go	65.62% <0.00%> (-2.95%)	⬇️
echo.go	83.58% <0.00%> (-2.36%)	⬇️
middleware/util.go	88.88% <0.00%> (-1.74%)	⬇️
response.go	85.18% <0.00%> (-1.66%)	⬇️
middleware/cors.go	77.94% <0.00%> (-1.52%)	⬇️
middleware/key_auth.go	66.66% <0.00%> (-1.13%)	⬇️
... and 18 more

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[lammel]

For references to external middlewares consider opening a PR in echo-contrib.

Closing this issue here.