fix so keyboard input works

Emscripen was hogging all keyboard events even when canvas didn't have
focus. There's an arcane way to fix that in js.

xwords4/wasm/Makefile

@@ -67,7 +67,7 @@ all: main.js
 # 		${INPUTS} -o $@
 
 # This isn't a thing any more
-main.html: ${INPUTS} $(MAKEFILE) shell_minimal.html
+main.html: ${INPUTS} Makefile shell_minimal.html
 	emcc $(DEFINES) -I . -I ../common -I ../relay -s USE_SDL=2 \
 		--preload-file assets_dir --shell-file shell_minimal.html \
 		-s USE_SDL_TTF=2 -s USE_SDL_IMAGE=2 -s SDL2_IMAGE_FORMATS='["png"]' \
@@ -76,9 +76,9 @@ main.html: ${INPUTS} $(MAKEFILE) shell_minimal.html
 		-s WASM=1 \
 		${INPUTS} -o $@
 
-install: main.html $(MAKEFILE)
+install: main.html
 	if [ -n "${XW_WASM_DEST}" ]; then \
-		for FILE in ${OUTPUTS} paho-mqtt.jspi xwutils.js; do \
+		for FILE in ${OUTPUTS} paho-mqtt.js xwutils.js; do \
 			[ -f $$FILE ] && scp $$FILE ${XW_WASM_DEST}; \
 			echo "$$FILE copied"; \
 		done; \

xwords4/wasm/main.c

@@ -1,4 +1,4 @@
-/* -*- compile-command: "cd ../wasm && make MEMDEBUG=TRUE main.html -j3"; -*- */
+/* -*- compile-command: "cd ../wasm && make MEMDEBUG=TRUE install -j3"; -*- */
 /*
  * Copyright 2021 by Eric House (xwords@eehouse.org).  All rights reserved.
  *

xwords4/wasm/shell_minimal.html

@@ -129,7 +129,8 @@
       let arguments = window.location.search.replaceAll('?', '').trim().split('&');
 
       var Module = {
-        preRun: [],
+        // preRun: see https://stackoverflow.com/questions/45936800/emscripten-canvas-jquery-toggle-focus/46083467
+        preRun: [function () {ENV.SDL_EMSCRIPTEN_KEYBOARD_ELEMENT = "#canvas";}],
         postRun: [],
         arguments: arguments,
         print: (function() {