update readme

Makefile

@@ -1,5 +1,5 @@
 watch:
-	./watch_compile.sh
+	./watch_compile.sh $(word 2,$(MAKECMDGOALS))
 
 html:
 	./scripts/slides_to_html.sh slides.md

README.md

@@ -3,3 +3,23 @@
 This repos aims to show a structured way to generate an html/pdf slideshow from markdown files
 
 it depends on `pandoc` for compiling to pdf/html and `inotify-tools` for watching changes.
+
+## Usage
+
+### Slides in  HTML/RevealJS:
+
+- `make html`: for creating the html file
+- `make serve_html`: for launching the server, then open [https://localhost:7777](https://localhost:7777) on your browser
+
+
+
+### Slides in PDF/LateX:
+
+- `make pdf`: for creating the pdf file
+
+Then open the pdf file in your favorite pdf reader
+
+
+### Compiling the slideset when modifications occur
+
+- `make watch` should launch an inotiy loop recompiling a pdf by default (for html, launch: `make watch html`)