docs: clarify special characters for key (#3642)
docs: clarify special characters for key (#3642)

Fixes #3638.

Signed-off-by: Hongbo Miao <bd0b003733b19656c9e63392d8681d3c4f910127@outlook.com>
tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa