osx/*: update page (#7665)

pages/common/oathtool.md

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+# oathtool
+
+> OATH one-time password tool.
+> More information: <https://www.nongnu.org/oath-toolkit/oathtool.1.html>.
+
+- Generate TOTP token (behaves like Google Authenticator):
+
+`oathtool --totp --base32 "{{secret}}"`
+
+- Generate a TOTP token for a specific time:
+
+`oathtool --totp --now "{{2004-02-29 16:21:42}}" --base32 "{{secret}}"`
+
+- Validate a TOTP token:
+
+`oathtool --totp --base32 "{{secret}}" "{{token}}"`