github-ci: enable the goimports linter

goimports[1] helps to sort imports in the same order. In addition to
fixing imports, it also formats the code in the same style as gofmt.
goimports linter for golangci-lint[2] provides checks for this
formatter.

1. https://pkg.go.dev/golang.org/x/tools/cmd/goimports
2. https://golangci-lint.run/usage/linters/

Author: oleg-jukovec

.github/workflows/check.yaml

@@ -47,4 +47,4 @@ jobs:
           # The `//nolint` workaround was not the acceptable way of warnings suppression,
           # cause those comments get rendered in documentation by godoc.
           # See https://github.com/tarantool/go-tarantool/pull/160#discussion_r858608221
-          args: -E gofmt -D errcheck
+          args: -E goimports -D errcheck

CONTRIBUTING.md

@@ -42,7 +42,7 @@ To check if the current changes will pass the linter in CI, install
 golnagci-lint from [sources](https://golangci-lint.run/usage/install/)
 and run it with next flags:
 ```bash
-golangci-lint run -E gofmt -D errcheck
+golangci-lint run -E goimports -D errcheck
 ```
 
 ## Benchmarking