added examples to FileInfoTool

ctapipe/tools/fileinfo.py

@@ -30,6 +30,17 @@ class FileInfoTool(Tool):
     """Extract metadata and other information from ctapipe output files"""
 
     name = "ctapipe-fileinfo"
+    description = __doc__
+    examples = """To get YAML output of all metadata in HDF5 files in the
+    current directory
+
+    > ctapipe fileinfo *.h5
+
+    Generate an index table of all metadata: Note that you can
+    use any table format allowed by astropy.table. However, formats
+    with metadata like fits or ecsv are recommended.
+
+    > ctapipe fileinfo --output-table index.fits *.h5"""
 
     input_files = traits.List(
         traits.Path(exists=True, directory_ok=False),