Sync poc to spec

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

poc/examples/pdfeditor/pdfeditor.pow

@@ -17,4 +17,4 @@
 #
 
 kroute add -X POST --entrypoint ./topdf '/editor/pdf' 
-kroute add / -c 'response /header/Content-Type text/html && response /body < pdfeditor.html'
+kroute add / -c 'response /headers/Content-Type text/html && response /body < pdfeditor.html'

poc/examples/pdfeditor/topdf

@@ -19,7 +19,7 @@
 tmpfile=$(mktemp --suffix=.pdf)
 pandoc --from=$(request /form/from) --to=pdf --output=${tmpfile} -t latex =(request /form/content)
 if [ $? -eq 0 ]; then
-	response /header/Content-Type application/pdf
+	response /headers/Content-Type application/pdf
 	response /body < ${tmpfile}
 	response /status 200
 else