change photon to aphoton (#476)

* change photon to aphoton

* fix test

* photon docs

* update doc

Co-authored-by: Federico Kunze <federico.kunze94@gmail.com>

docs/basics/README.md

@@ -11,5 +11,6 @@ This repository contains reference documentation on the basic concepts of Etherm
 1. [Accounts](./accounts.md)
 2. [Gas and Fees](./gas.md)
 3. [Lifecycle of a transaction](./transactions.md)
+4. [Photon](./photon.md)
 
 After reading the basics, head on to the [Core Reference](../core/README.md) for more advanced material.

docs/basics/gas.md

@@ -26,4 +26,4 @@ The `AnteHandler` is a special `handler` that is run for every transaction durin
 
 ## Next {hide}
 
-Learn about the [encoding](./../core/encoding.md) formats used on Ethermint {hide}
+Learn about the [Photon](./photon.md) token {hide}

docs/basics/photon.md

@@ -0,0 +1,33 @@
+<!--
+order: 4
+-->
+
+# Photon
+
+Learn about the Photon, Ethermint's staking token. {synopsis}
+
+## Introduction
+
+::: tip
+The photon's initial distribution and supply is still TBD and will be announced in the future.
+:::
+
+The photon is the staking token used in Ethermint.
+
+## Base Denomination
+
+Ethermint uses [Atto](https://en.wikipedia.org/wiki/Atto-) Photon as the base denomination to maintain parity with Ethereum.
+
+```
+1 photon = 1×10⁻¹⁸ aphoton
+```
+
+This matches Ethereum denomination of:
+
+```
+1 ETH = 1x10⁻¹⁸ wei
+```
+
+## Next {hide}
+
+Learn about the [encoding](./../core/encoding.md) formats used on Ethermint {hide}