add security writeups and dev tools link

[computerality]

No description provided.

[dguido]

Looks good, add an entry to the Table of Contents. Maybe there are a few other historical writeups that everyone should be familiar with. Maybe an old Hacking Distributed writeup on the DAO hack and similar stuff?

[computerality]

Added toc. There are definitely other good ones but I don't have links handy. Can do them in a later commit.

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