Add golangci linter configuration

[aldas]

Relates to: #2924

NB: it does not fix couple of staticcheck problems that are being reported

[x@x echo]$ golangci-lint run 
bind.go:158:6: QF1001: could apply De Morgan's law (staticcheck)
                if !(isElemSliceOfStrings || isElemString || isElemInterface) {
                   ^
middleware/basic_auth.go:124:8: QF1001: could apply De Morgan's law (staticcheck)
                                if !(len(auth) > l+1 && strings.EqualFold(auth[:l], basic)) {
                                   ^
middleware/static.go:253:8: QF1001: could apply De Morgan's law (staticcheck)
                                if !(errors.As(err, &he) && config.HTML5 && he.StatusCode() == http.StatusNotFound) {
                                   ^
route.go:88:4: QF1012: Use fmt.Fprintf(...) instead of WriteString(fmt.Sprintf(...)) (staticcheck)
                        uri.WriteString(fmt.Sprintf("%v", pathValues[n]))
                        ^
router.go:998:30: QF1008: could remove embedded field "RouteInfo" from selector (staticcheck)
                rPath = matchedRouteMethod.RouteInfo.Path

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.01%. Comparing base (19364e2) to head (cd9cb37).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2930   +/-   ##
=======================================
  Coverage   93.01%   93.01%           
=======================================
  Files          43       43           
  Lines        4496     4498    +2     
=======================================
+ Hits         4182     4184    +2     
  Misses        196      196           
  Partials      118      118           

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