Adds some links to handy tools. (#208)

* Adds some links to handy tools.

Closes #192.

* Removes 2nd level header. Not needed.

Author: johnnymatthews

content/reference/tools.md

@@ -0,0 +1,22 @@
+---
+title: "Tools"
+lead: "A list of useful tools, workflows, and projects that can help developers build with Entropy."
+---
+
+## Polkadot Chain Explorer
+
+[polkadot.js.org/apps](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Ftestnet.entropy.xyz#/explorer)
+
+A one-size-fits-all blockchain explorer for Substrate-based chains, built by the [Polkadot.js team](https://polkadot.js.org/).
+
+## Testnet Status
+
+[status.entropy.xyz](https://status.entropy.xyz/)
+
+A constantly updated list of registered accounts, programs, and validators.
+
+## Uptime
+
+[uptime.entropy.xyz](https://entropydotxyz.statuspage.io/)
+
+The home of Entropy's real-time and historical data on system performance.