Merge pull request #429 from brynnelliott/patch-10

Added alt text to images

episodes/00-intro.Rmd

@@ -204,7 +204,7 @@ open without them interfering with each other.
 
 Let's take a quick tour of RStudio.
 
-![RStudio_startup](../fig/R_00_Rstudio_01.png)
+![Screenshot of the RStudio_startup screen](../fig/R_00_Rstudio_01.png)
 
 RStudio is divided into four "panes". The placement of these
 panes and their content can be customized (see menu, Tools -> Global Options ->
@@ -363,15 +363,15 @@ You can see if you have a package installed by looking in the `packages` tab
 (on the lower-right by default). You can also type the command
 `installed.packages()` into the console and examine the output.
 
-![Packages pane](../fig/packages_pane.png)
+![Screenshot of Packages pane](../fig/packages_pane.png)
 
 Additional packages can be installed from the ‘packages’ tab.
 On the packages tab, click the ‘Install’ icon and start typing the
 name of the package you want in the text box. As you type, packages
 matching your starting characters will be displayed in a drop-down
 list so that you can select them.
 
-![Install Packages Window](../fig/R_00_Rstudio_03.png)
+![Screenshot of Install Packages Window](../fig/R_00_Rstudio_03.png)
 
 At the bottom of the Install Packages window is a check box to
 ‘Install’ dependencies. This is ticked by default, which is usually