doc: add default bitcoin.conf locations

Added default bitcoin.conf data directories and paths
Added example bitcoin.conf link

doc/bitcoin-conf.md

@@ -50,3 +50,13 @@ rpcport=4000
 The configuration file is not automatically created; you can create it using your favorite text editor. By default, the configuration file name is `bitcoin.conf` and it is located in the Bitcoin data directory, but both the Bitcoin data directory and the configuration file path may be changed using the `-datadir` and `-conf` command-line options.
 
 The `includeconf=<file>` option in the `bitcoin.conf` file can be used to include additional configuration files.
+
+### Default configuration file locations
+
+Operating System | Data Directory | Example Path
+-- | -- | --
+Windows | `%APPDATA%\Bitcoin\` | `C:\Users\username\AppData\Roaming\Bitcoin\bitcoin.conf`
+Linux | `$HOME/.bitcoin/` | `/home/username/.bitcoin/bitcoin.conf`
+macOS | `$HOME/Library/Application Support/Bitcoin/` | `/Users/username/Library/Application Support/Bitcoin/bitcoin.conf`
+
+You can find an example bitcoin.conf file in [share/examples/bitcoin.conf](../share/examples/bitcoin.conf).