docs(README): add documentation on how to use the api

Author: danvergara

README.md

@@ -44,6 +44,8 @@ docker run --rm -p 8080:8080 -v /tmp:/tmp ghcr.io/danvergara/morphos-server:late
 
 ## Usage
 
+### HTML form
+
 Run the server as mentioned above and open up your favorite browser. You'll see something like this:
 
 <img src="screenshots/morphos.png"/>
@@ -68,6 +70,36 @@ A modal will pop up with a preview of the converted image.
 
 <img src="screenshots/modal_morphos.png"/>
 
+### API
+
+You can consume morphos through an API, so other systems can integrate with it.
+
+##### Endpoints
+
+`GET /api/v1/formats`
+
+This returns a JSON that shows the supported formats at the moment.
+
+e.g.
+
+```
+{"documents": ["docx", "xls"], "image": ["png", "jpeg"]}
+```
+
+`POST /api/v1/upload`
+
+This is the endpoint that converts files to a desired format. It is basically a multipart form data in a POST request. The API simply writes the converted files to the response body.
+
+e.g.
+
+```
+ curl -F 'targetFormat=epub' -F 'uploadFile=@/path/to/file/foo.pdf' localhost:8080/api/v1/upload --output foo.epub
+```
+The form fields are:
+
+* targetFormat: the target format the file will be converted to
+* uploadFile: The path to the file that is going to be converted
+
 ### Configuration
 
 The configuration is only done by the environment varibles shown below.