Added note about optional API key environment variable

README.md

@@ -7,18 +7,22 @@
 ![Example Setup](https://raw.githubusercontent.com/Chadsr/waybar-crypto/master/images/waybar_crypto.png)
 
 ### Requirements
+
 - Python 3.6 or greater
 - python-requests
 
 ### Installation
+
 1. Clone this repo into the waybar modules directory
+
 ```
 cd ~/.config/waybar/modules
 git clone https://github.com/Chadsr/waybar-crypto.git crypto
 pip install --user -r requirements.txt
 ```
 
 2. Then in your waybar config (e.g. `~/.config/waybar/config`)
+
 ```
 "custom/crypto": {
     "format": "{}",
@@ -30,12 +34,14 @@ pip install --user -r requirements.txt
 ```
 
 3. Install the needed fonts
+
 ```
 curl -O https://github.com/AllienWorks/cryptocoins/blob/master/webfont/cryptocoins.ttf
 cp cryptocoins.ttf /usr/share/fonts/TTF # Or some font path of your choice
 ```
 
 ### Configuration
+
 The information displayed can be customised by editing the crypto.ini configuration file.
 (e.g. `~/.config/waybar/modules/crypto/crypto.ini` if you followed the instructions above)
 
@@ -52,20 +58,24 @@ icon = 
 [eth]
 icon = 
 ```
+
 - **currency:** Any valid currency code should be accepted
 - **currency_symbol:** A corresponding symbol of the currency you wish to display
-- **display:** A list of metrics you wish to display for each crypto currency. No spaces. 
-
-    Valid options are:
-    - **price:** Displays the current price.
-    - **change1h:** Displays the price change over the past hour.
-    - **change24h:** Displays the price change over the past 24 hours.
-    - **change7d:** Displays the price change over the past week.
-    - **volume24h:** Displays the volume in your chosen currency, over the past 24 hours.
+- **display:** A list of metrics you wish to display for each crypto currency. No spaces.
+  Valid options are:
+  - **price:** Displays the current price.
+  - **change1h:** Displays the price change over the past hour.
+  - **change24h:** Displays the price change over the past 24 hours.
+  - **change7d:** Displays the price change over the past week.
+  - **volume24h:** Displays the volume in your chosen currency, over the past 24 hours.
 - **api_key:** CoinmarketCap API key obtained from their [new api](https://coinmarketcap.com/api/) (The public API is discontinuing :'()
 
+_Alternatively, the CoinMarketCap API key can be set through the environment variable `COINMARKETCAP_API_KEY`, if you do not wish to save it to the crypto.ini file._
+
 #### Adding cryptocurrencies:
-For each cryptocurrency you wish to display, add a section as shown in the example above, where the section name is the **short** cryptocurrency name. 
+
+For each cryptocurrency you wish to display, add a section as shown in the example above, where the section name is the **short** cryptocurrency name.
 
 Valid options:
+
 - **icon:** A character symbol to display next to this cryptocurrency's metrics.