pgsql: doc: Add more ICU rules examples

doc: Add more ICU rules examples

In particular, add an example EBCDIC collation.

Author: Daniel Verite <daniel@manitou-mail.org>
Discussion: https://www.postgresql.org/message-id/flat/35cc1684-e516-4a01-a256-351632d47066@manitou-mail.org

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/103df207a71e74d64173edcb7bacec872933755b

Modified Files
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doc/src/sgml/charset.sgml              | 58 +++++++++++++++++++++++++++++++++-
doc/src/sgml/ref/create_collation.sgml | 13 +++-----
doc/src/sgml/ref/create_database.sgml  |  4 +--
3 files changed, 62 insertions(+), 13 deletions(-)