feat: allow struct slice and struct array for valueType (#70)

* feat: allow struct slice and struct array for to determine Header

feat: add AlignRecord flag to Decoder

Closes: #63

doc: update comments

Merge pull request #54 from hori-ryota/fix-nested-prefix-order

fix: nexted prefix order with inline

chore: update CI to use Go1.18

feat: Add Decoder.NormalizeHeader

Closes: #45

chore: Adjust for Go1.17

- update actions to use Go1.17
- add test file with build tag for Go1.17 due to
  csv.ParseError.Column being now 1-indexed

Update actions to use Go1.16

Adjust tests for older Go versions

Support inline tag in Header function