rump documentation for srfi-9

docs/api/srfi/9.md

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+# SRFI 9 - Defining record types
+
+The `(srfi 9)` library provides support for defining record types. See
+the [SRFI document](http://srfi.schemers.org/srfi-9/srfi-9.html) for
+more information.
+
+- `record?`
+- `define-record-type`
+- `register-simple-type`
+- `make-type-predicate`
+- `make-constructor`
+- `make-getter`
+- `make-setter`
+- `slot-set!`
+- `type-slot-offset`