Explicitly mention .image and .figuer objects

See https://github.com/jsvine/pdfplumber/issues/219

README.md

@@ -84,7 +84,7 @@ The `pdfplumber.Page` class is at the core of `pdfplumber`. Most things you'll d
 |`.page_number`| The sequential page number, starting with `1` for the first page, `2` for the second, and so on.|
 |`.width`| The page's width.|
 |`.height`| The page's height.|
-|`.objects` / `.chars` / `.lines` / `.rects`| Each of these properties is a list, and each list contains one dictionary for each such object embedded on the page. For more detail, see "[Objects](#objects)" below.|
+|`.objects` / `.chars` / `.lines` / `.rects` / `.curves` / `.figures` / `.images`| Each of these properties is a list, and each list contains one dictionary for each such object embedded on the page. For more detail, see "[Objects](#objects)" below.|
 
 ... and these main methods:
 
@@ -107,6 +107,8 @@ Each instance of `pdfplumber.PDF` and `pdfplumber.Page` provides access to four
 - `.lines`, each representing a single 1-dimensional line.
 - `.rects`, each representing a single 2-dimensional rectangle.
 - `.curves`, each representing a series of connected points.
+- `.images`, each representing an image.
+- `.figures`, each representing a figure.
 
 Each object is represented as a simple Python `dict`, with the following properties:
 
@@ -185,6 +187,14 @@ Each object is represented as a simple Python `dict`, with the following propert
 
 Additionally, both `pdfplumber.PDF` and `pdfplumber.Page` provide access to two derived lists of objects: `.rect_edges` (which decomposes each rectangle into its four lines) and `.edges` (which combines `.rect_edges` with `.lines`). 
 
+#### `image` properties
+
+[To be completed.]
+
+#### `figure` properties
+
+[To be completed.]
+
 ## Visual debugging
 
 __Note:__ To use `pdfplumber`'s visual-debugging tools, you'll also need to have two additional pieces of software installed on your computer: