build: clone repository "docs" and configuration when syncing project docs (#145)

* removes no longer wanted files

* adds sidebar.js

* readds commands

* adds sidebar.json

---------

Co-authored-by: Michael Brooks <mbrooks@slack-corp.com>

Author: lukegalbraithrussell

.github/workflows/sync-docs-from-cli-repo.yml

@@ -0,0 +1,55 @@
+[
+    {
+        "type": "doc",
+        "id": "slack-cli/index",
+        "label": "Slack CLI",
+        "className": "sidebar-title"
+    },
+    { "type": "html", "value": "<hr>" },
+    {
+        "type": "category",
+        "label": "Guides",
+        "collapsed": false,
+        "items": [
+            "slack-cli/guides/installing-the-slack-cli-for-mac-and-linux",
+            "slack-cli/guides/installing-the-slack-cli-for-windows",
+            "slack-cli/guides/authorizing-the-slack-cli",
+            "slack-cli/guides/using-slack-cli-with-bolt-frameworks",
+            "slack-cli/guides/using-slack-cli-on-an-enterprise-grid-organization",
+            "slack-cli/guides/running-slack-cli-commands",
+            "slack-cli/guides/using-environment-variables-with-the-slack-cli",
+            "slack-cli/guides/troubleshooting-slack-cli-errors",
+            "slack-cli/guides/setting-up-ci-cd-with-the-slack-cli",
+            "slack-cli/guides/deploying-with-the-slack-cli-and-github-actions",
+            "slack-cli/guides/uninstalling-the-slack-cli"
+        ]
+    },
+    { "type": "html", "value": "<hr>" },
+    {
+        "type": "category",
+        "label": "Reference",
+        "collapsed": false,
+        "items": [
+            {
+                "type": "category",
+                "label": "Commands",
+                "items": [
+                    {
+                        "type": "autogenerated",
+                        "dirName": "slack-cli/reference/commands"
+                    }
+                ]
+            },
+            {
+                "type": "doc",
+                "id": "slack-cli/reference/errors",
+                "label": "Errors"
+            },
+            {
+                "type": "doc",
+                "id": "slack-cli/reference/experiments",
+                "label": "Experiments"
+            }
+        ]
+    }
+]