Doxygen: rename all .dox files to end with .md

Using a standard ending here will let other tools that expect
markdown understand our output here.

This commit was automatically generated with:

   for fn in $(find src -name '*.dox'); do \
      git mv "$fn" "${fn%.dox}.md"; \
   done

1 files changed, 14 insertions, 0 deletions

diff --git a/src/lib/pubsub/lib_pubsub.md b/src/lib/pubsub/lib_pubsub.md
new file mode 100644
index 0000000000..3f4c473436
--- /dev/null
+++ b/src/lib/pubsub/lib_pubsub.md
@@ -0,0 +1,14 @@
+@dir /lib/pubsub
+@brief lib/pubsub: Publish-subscribe message passing.
+
+This module wraps the \refdir{lib/dispatch} module, to provide a more
+ergonomic and type-safe approach to message passing.
+
+In general, we favor this mechanism for cases where higher-level modules
+need to be notified when something happens in lower-level modules. (The
+alternative would be calling up from the lower-level modules, which
+would be error-prone; or maintaining lists of function-pointers, which
+would be clumsy and tend to complicate the call graph.)
+
+See pubsub.c for more information.
+