doc(README): fix descriptions of new examples

Author: Damian Rouson

README.md

@@ -45,12 +45,30 @@ fpm run --example
 ```
 Please report any test failures by submitting an [issue] on the DAG repository.
 
-Example
--------
+Examples
+--------
+
+The [example] subdirectory provides the following examples:
 
-The [./example/feats-dependency-tree.f90] program provides an example of the use of dag to
-describe the module dependencies in an early version of the Framework for Extensible Asynchronous 
-Task Scheduling ([FEATS]).  The example also writes the following image to a `.pdf` file:
+* [print-to-json.f90] - constructs and prints it a JSON representation the DAG. 
+  Run this example and redirect the output to a file as follows:
+```
+fpm run --example print-to-json > dag.json
+```
+* [read-from-json.f90] - constructs a DAG by reading from a JSON file.
+  Run this example as follows:
+```
+fpm run --example read-from-json > dag.json
+```
+* [dag-to-dot.f90] - constructs a DAG describing the module dependencies in  
+  an early version of the Framework for Extensible Asynchronous 
+  Task Scheduling ([FEATS]) and prints the DAG to a .dot file suitable for
+  conversion to a `.pdf` as follows:
+```
+fpm run --example dag-to-dot > feats-dag.dot
+dot -Tpdf -o feats.pdf feats.dot
+```
+which should produce the graph below.
 
 ![feats-dependencies](https://user-images.githubusercontent.com/13108868/133311851-721b7cda-1d10-4ee1-a51d-6169ca624839.png)
 
@@ -75,6 +93,9 @@ This library is released under a [BSD-3 license].
 [JSON]: https://www.json.org/json-en.html
 [jsonff]: https://gitlab.com/everythingfunctional/jsonff
 [./src/dag_test.f90]: ./src/dag_test.f90
-[./example/feats-dependency-tree.f90]: ./example/feats-dependency-tree.f90
+[example]: ./example/
 [FEATS]: https://github.com/sourceryinstitute/feats
 [Assert]: https://github.com/sourceryinstitute/assert
+[print-to-json.f90]: ./example/print-to-json.f90
+[read-from-json.f90]:./example/read-from-json.f90
+[dag-to-dot.f90]: ./example/dag-to-dot.f90