Sort HTML_DST output

Author: mawds

Makefile

@@ -75,9 +75,9 @@ HTML_DST = \
   ${DST}/index.html \
   ${DST}/conduct/index.html \
   ${DST}/setup/index.html \
-  $(patsubst _episodes/%.md,${DST}/%/index.html,$(wildcard _episodes/*.md)) \
+  $(patsubst _episodes/%.md,${DST}/%/index.html,$(sort $(wildcard _episodes/*.md))) \
   ${DST}/reference/index.html \
-  $(patsubst _extras/%.md,${DST}/%/index.html,$(wildcard _extras/*.md)) \
+  $(patsubst _extras/%.md,${DST}/%/index.html,$(sort $(wildcard _extras/*.md))) \
   ${DST}/license/index.html
 
 ## lesson-md        : convert Rmarkdown files to markdown