Task: Add docs on keys with dots

Adds documentation on how to use a key lookup indicator for dealing
with keys that have dots when specifying a path as part of create,
read, and write commands.

Resolves: #22

mkdocs/snippets/keys_with_dots.md

@@ -0,0 +1,17 @@
+### Keys with dots
+When specifying a key that has a dot use key lookup indicator.
+
+```yaml
+b:
+  foo.bar: 7
+```
+
+```bash
+yaml r sample.yaml b[foo.bar]
+```
+
+```bash
+yaml w sample.yaml b[foo.bar] 9
+```
+
+Any valid yaml key can be specified as part of a key lookup.