Add note about adding portfolio buy-price to coins

docs/content/faq.md

@@ -184,6 +184,29 @@ draft: false
 
   Your portfolio is autosaved after you edit holdings. You can also press <kbd>ctrl</kbd>+<kbd>s</kbd> to manually save your portfolio holdings to the config file.
 
+## How do I include buy/cost price in my portfolio?
+
+  Currently there is no UI for this.  If you want to include the cost of your coins in the Portfolio screen, you will need to edit your config.toml
+
+  Each coin consists of four values:  coin name, coin amount, cost-price, cost-currency.
+
+  For example, the following configuration includes 100 ALGO at USD1.95 each; and 0.1 BTC at AUD50100.83 each. 
+
+  ```toml
+   holdings = [["Algorand", "100", "1.95", "USD"], ["Bitcoin", "0.1", "50100.83", "AUD"]]
+   ```
+
+  With this configuration, four new columns are useful:
+
+  - `cost_price` the price and currency that the coins were purchased at
+  - `cost` the cost (in the current currency) of the coins
+  - `profit` the PNL of the coins (current value vs original cost)
+  - `profit_percent` the PNL of the coins as a fraction of the original cost
+
+  With the holdings above, and the currency set to GBP (British Pounds) cointop will look something like this:
+  
+  ![Screen Shot 2021-10-22 at 8 41 21 am](https://user-images.githubusercontent.com/122371/138361142-8e1f32b5-ca24-471d-a628-06968f07c65f.png)
+
 ## How do I hide my portfolio balances (private mode)?
 
   You can run cointop with the `--hide-portfolio-balances` flag to hide portfolio balances or use the keyboard shortcut <kbd>Ctrl</kbd>+<kbd>space</kbd> on the portfolio page to toggle hide/show.
@@ -505,4 +528,4 @@ draft: false
   DEBUG=1 DEBUG_HTTP=1 cointop
   ```
 
-  If you set environment variable `DEBUG_FILE` you can explicitly provide a logfile location, rather than `/tmp/cointop.log`
+  If you set environment variable `DEBUG_FILE` you can explicitly provide a logfile location, rather than `/tmp/cointop.log`