Implement documentation for cache:clear

Relates to https://github.com/PeteBishwhip/native-cli/issues/11

Author: Pete Bishop

Writerside/n.tree

@@ -13,6 +13,7 @@
     </toc-element>
     <toc-element toc-title="Commands">
         <toc-element topic="New.md"/>
+        <toc-element topic="cache-clear.md"/>
         <toc-element topic="check-update.md"/>
         <toc-element topic="update.md"/>
     </toc-element>

Writerside/topics/cache-clear.md

@@ -0,0 +1,34 @@
+# cache:clear
+
+NativeCLI uses some files to cache data that does not need to be retrieved on every invocation.
+Sometimes, it may be preferable to clear these caches to ensure that the latest data is used.
+
+<tip>
+This command is only available in NativeCLI version 1.0.0-rc.1 and later.
+</tip>
+
+## Command
+
+Syntax:
+
+```shell
+nativecli cache:clear [OPTIONS]
+```
+
+## Options
+
+Describe what each option is used for:
+
+-c, --cache
+: Select a specific cache to clear. If not specified, all caches will be cleared.
+
+-n, --non-interactive
+: Clears the specified caches without prompting for confirmation.
+
+## Available Caches
+
+A cache is only considered "available" once it has data within. If the cache doesn't yet exist, you'll receive a
+message indicating that the cache is empty.
+
+version
+: The latest versions of NativeCLI and NativePHP that are available. This cache expires hourly.