Update index.md

add image (and a couple of commas!)

index.md

@@ -4,17 +4,19 @@ title: Introduction to SimPEG using an example with electrical resistivity tomog
 
 +++ { "part": "abstract" }
 Geophysical inversions are used to build models of the subsurface from data collected over the Earth. Solving an inverse problem and obtaining a meaningful result requires bringing together numerical tools for solving partial differential equations, formulating an optimization problem, and specifying tuning parameters and heuristics for performing the optimization. All of these choices are what make an inversion work (or not) in practice. These are captured in the software that implements the inversion.
-In this workshop we'll showcase how we can use the tools available in
+In this workshop, we'll showcase how we can use the tools available in
 [SimPEG][https://simpeg.xyz], a Python library for Simulations and Parameter
 Estimations in Geophysics, to simulate Electrical Resistivity Tomography (a.k.a. ERT / DC resistivity) data from
 a synthetic model and then to run a deterministic inversion to recover the
 original model.
 You'll learn how to set up a DC survey, define a mesh, build a synthetic model,
 create a simulation that implements all the physics, and run a forward
-model to generate synthetic data. Lastly you'll learn how to set up an
+model to generate synthetic data. Lastly, you'll learn how to set up an
 inversion to recover the resistivity of the subsurface.
-By the end of the tutorial you'll be able to use SimPEG to invert your own
+By the end of the tutorial, you'll be able to use SimPEG to invert your own
 All of the simulation types that are available within SimPEG (gravity, magnetics, electromagnetics, etc.) are built with the same common framework, meaning many of the concepts illustrated in this tutorial are transferrable to other data types. 
+
+![dc-resistivity-inversion](images/dc-inversion-image.png)
 +++
 
 ## Prerequisites