add rump documentation for srfi-27

docs/api/srfi/27.md

@@ -0,0 +1,17 @@
+# SRFI 27 - Sources of random bits
+
+The `(srfi 27)` library provides sources of random bits. See the
+[SRFI document](http://srfi.schemers.org/srfi-27/srfi-27.html) for
+more information.
+
+- `random-integer`
+- `random-real`
+- `default-random-source`
+- `make-random-source`
+- `random-source?`
+- `random-source-state-ref`
+- `random-source-state-set!`
+- `random-source-randomize!`
+- `random-source-pseudo-randomize!`
+- `random-source-make-integers`
+- `random-source-make-reals`