added readme to mention submodule

made the build script auto-update the wiki submodule

.gitmodules

@@ -2,3 +2,5 @@
 	path = src/wiki
 	url = https://tildegit.org/cafe/wiki
 	branch = HEAD
+[submodule "wiki"]
+	branch = main

README.md

@@ -0,0 +1,4 @@
+after cloning, make sure to
+	git submodule init
+	git submodule update
+the build script will also update the wiki submodule on each run

build.sh

@@ -2,6 +2,8 @@
 
 #umask 0113
 
+git submodule update
+
 #. in reference to src/
 for path in . ./wiki;do
   tmpindex=$(mktemp --suffix '.md')  # for generating list of markdown links for index.html