edited readme file

Figures generated using "display_content.py" from StatProofBookTools are now displayed in the readme file.

Author: StatProofBook

README.md

@@ -7,3 +7,11 @@
 This is the GitHub repository of **The Book of Statistical Proofs**, available from [StatProofBook.github.io](https://statproofbook.github.io/), i.e. the repository that has to be forked when a new proof is to be added or when the website has to be edited in any other way. In order to avoid redundancies, all relevant [information about the project](https://statproofbook.github.io/about/) as well as a [guide how to contribute](https://statproofbook.github.io/contribute/) are given on the website itself (and in [the wiki of this repository](https://github.com/StatProofBook/StatProofBook.github.io/wiki)).
 
 Unless otherwise noted, all content in this repository is licensed under the ![CC-BY-SA compact icon](https://licensebuttons.net/l/by-sa/4.0/80x15.png) [Creative Commons Attribution-ShareAlike 4.0 International Public License](https://github.com/StatProofBook/StatProofBook.github.io/blob/master/LICENSE.md). Read the [license summary](https://github.com/StatProofBook/StatProofBook.github.io/blob/master/LICENSE_short.md) for more details.
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+<br>
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+### Gallery: StatProofBook Contents
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+<img src="https://raw.githubusercontent.com/StatProofBook/StatProofBookTools/master/display_content/Content.png" alt="Content by Type" width=500> <img src="https://raw.githubusercontent.com/StatProofBook/StatProofBookTools/master/display_content/Development.png" alt="Development over Time" width=500>
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+<img src="https://raw.githubusercontent.com/StatProofBook/StatProofBookTools/master/display_content/Topic_Definitions.png" alt="Definitions by Topic" width=1000> <img src="https://raw.githubusercontent.com/StatProofBook/StatProofBookTools/master/display_content/Topic_Proofs.png" alt="Proofs by Topic" width=1000>