chore: fix license headers

[aasseman]

Fixes #74

[github-actions[bot]]

Coverage after merging fix_license_headers into main will be

84.69%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
tap_aggregator/src
aggregator.rs	92.45%	100%	100%	90.70%	40–43, 53–56
main.rs	5.56%	100%	11.11%	3.70%	12, 16–18, 20, 24–25, 28–30, 33, 36–41, 44–48, 50
server.rs	90.63%	100%	100%	87.76%	51–55, 68
tap_core/src
eip_712_signed_message.rs	83.78%	100%	80%	85.19%	56
lib.rs	87.50%	100%	87.50%	87.50%	17
receipt_aggregate_voucher.rs	92.11%	100%	85.71%	93.55%	21
tap_core/src/adapters/test
collateral_adapter_mock.rs	82.98%	100%	71.43%	85%	28–29, 47, 53–55
collateral_adapter_test.rs	100%	100%	100%	100%
rav_storage_adapter_mock.rs	94.74%	100%	83.33%	96.88%	10
rav_storage_adapter_test.rs	100%	100%	100%	100%
receipt_checks_adapter_mock.rs	87.18%	100%	83.33%	87.88%	52, 56–58
receipt_checks_adapter_test.rs	95.83%	100%	100%	95%	56
receipt_storage_adapter_mock.rs	97.37%	100%	92.31%	98.41%	10
receipt_storage_adapter_test.rs	100%	100%	100%	100%
tap_core/src/tap_receipt
mod.rs	66.67%	100%	50%	75%
receipt.rs	79.41%	100%	77.78%	80%	20, 44
received_receipt.rs	82.42%	100%	75.86%	83.82%	100–102, 109–111, 113–115, 160, 171, 185–187, 95–97

[ColePBryan]

@aasseman I know I always ask this, but is there a way to automate checking for spdx headers/ copyright headers? It is obviously something easy to miss.