Add guides section to the site

[polymutex]

Now that we have the mitmproxy guide (one of multiple planned guides, see #170 for others), we should put these guides on the Walletbeat website itself.

This way we can link to such guides in the "methodology" section of the relevant attributes. For example, the attribute on wallet address privacy would link to the mitmproxy guide in order to explain how the data is collected.