bug: go1.17 support

Fuzzing tests are introduced in go1.18. When linter runs on older go runtime, it's ok, that testing.F is not found.

Disable f-checks if testing.F not found.

bug: support go1.17

bug: use deprecated types.NewSignature to support go1.17

docs: add notes about fuzzing tests

chore: fix typo

feat: support subtest builder as anonymous function and fixture method

docs: add excpetion section to README and describe tb support

chore: add basic golangci-lint configuration. (#23)

* chore: add a basic golangci-lint configuration.

feat: support testing.TB

fix: filter sub-test functions from thelper checks