Add copyright / licensing statement for VCF test data.

The bulk of the data comes from EBI's vcf-validator at
https://github.com/EBIvariation/vcf-validator

A few new ones have appeared since, and some appear to be of 1000
genomes origin.

test/vcf/LICENSE.md

@@ -0,0 +1,36 @@
+Copyright and licensing for the different files here varies by host
+institution that submitted the tests.
+
+test/vcf/*.vcf:
+    The vast bulk of the test files originated from European
+    Bioinformatics Institute's vcf-validator:
+    https://github.com/EBIvariation/vcf-validator/blob/master/LICENSE
+
+    These are Copyright EBI and the project is Apache 2.0 licensed.
+    See https://www.apache.org/licenses/LICENSE-2.0
+
+test/vcf/4.*/passed/complexfile_passed_000.vcf
+    Also present in the EBI vcf-validator, however this data looks to
+    be a subset of the 1000 Genomes project so it may be covered by
+    the 1000 genomes license instead (i.e. freely available under the
+    Fort Lauderdale Agreement).
+    See https://www.internationalgenome.org/IGSR_disclaimer
+    and https://www.internationalgenome.org/category/data-access/
+
+examples/vcf/simple.vcf
+    Part of commit 7aeed5b, but not from the vcf-validator.
+    Unknown copyright / license, but assumed to be 1000 Genomes.
+
+examples/vcf/sv44.vcf
+    Daniel Cameron 2022 0a7c47b
+
+test/vcf/4.3/failed/failed_body_format_007.vcf
+    Daniel Cameron 2023 dbf3f7b
+
+test/vcf/4.3/failed/failed_body_info_integer_overflow.vcf
+test/vcf/4.3/failed/failed_body_info_integer_reserved.vcf
+test/vcf/4.3/failed/failed_body_info_integer_underflow.vcf
+    Daniel Cameron 2023 09a3195
+
+test/vcf/4.5/passed/zero_length_LAA.vcf
+    Daniel Cameron 2024 8589eb6