Remove development and test files from the gem package

[orien]

There are a bunch of files in the gem package that aren't useful for downstream projects. Removing these reduces the gem package size from 110K to 77K!

gem contents diff

< .github/workflows/gem-push.yml
< .gitignore
< .rspec
< .vs/AvaTax-REST-V2-Ruby-SDK/v15/.suo
< .vs/VSWorkspaceState.json
< .vs/slnx.sqlite
< .yardopts
< Gemfile
  LICENSE
  README.md
< Rakefile
< avatax.gemspec
  example/avatax.rb
  example/credentials.example.yaml
  lib/avatax.rb
  lib/avatax/api.rb
  lib/avatax/client.rb
  lib/avatax/client/accounts.rb
  lib/avatax/client/addresses.rb
  lib/avatax/client/advancedrules.rb
  lib/avatax/client/ageverification.rb
  lib/avatax/client/avafileforms.rb
  lib/avatax/client/batches.rb
  lib/avatax/client/certexpressinvites.rb
  lib/avatax/client/certificates.rb
  lib/avatax/client/companies.rb
  lib/avatax/client/compliance.rb
  lib/avatax/client/contacts.rb
  lib/avatax/client/customers.rb
  lib/avatax/client/datasources.rb
  lib/avatax/client/definitions.rb
  lib/avatax/client/distancethresholds.rb
  lib/avatax/client/ecms.rb
  lib/avatax/client/ecommercetoken.rb
  lib/avatax/client/errortransactions.rb
  lib/avatax/client/filingcalendars.rb
  lib/avatax/client/filings.rb
  lib/avatax/client/firmclientlinkages.rb
  lib/avatax/client/free.rb
  lib/avatax/client/fundingrequests.rb
  lib/avatax/client/items.rb
  lib/avatax/client/jurisdictionoverrides.rb
  lib/avatax/client/locations.rb
  lib/avatax/client/multidocument.rb
  lib/avatax/client/nexus.rb
  lib/avatax/client/notices.rb
  lib/avatax/client/notifications.rb
  lib/avatax/client/onboarding.rb
  lib/avatax/client/pointofsale.rb
  lib/avatax/client/provisioning.rb
  lib/avatax/client/registrar.rb
  lib/avatax/client/reports.rb
  lib/avatax/client/settings.rb
  lib/avatax/client/shippingverification.rb
  lib/avatax/client/subscriptions.rb
  lib/avatax/client/taxContent/README.txt
  lib/avatax/client/taxRatesByZip/README.txt
  lib/avatax/client/taxcodes.rb
  lib/avatax/client/taxcontent.rb
  lib/avatax/client/taxprofiles.rb
  lib/avatax/client/taxrules.rb
  lib/avatax/client/transactions.rb
  lib/avatax/client/upcs.rb
  lib/avatax/client/userdefinedfields.rb
  lib/avatax/client/users.rb
  lib/avatax/client/utilities.rb
  lib/avatax/configuration.rb
  lib/avatax/connection.rb
  lib/avatax/request.rb
  lib/avatax/version.rb
< spec/avatax/client/accounts_spec.rb
< spec/avatax/client/transactions_spec.rb
< spec/avatax/request_spec.rb
< spec/avatax_spec.rb
< spec/credentials.yaml.example
< spec/fixtures/accounts.json
< spec/spec_helper.rb