Improvements to the doc (#1989)

* Added Overview page

* Revised Getting Started page

* Minor revision

* Edited readme, minor modifications to docs

* Removed sweep.yaml, .devcontainer, .ergomake

* Moved security.md to .github, added contributing.md

* changes as per code review

* updated contributing.md

* fixed broken links & added missing links in doc, improved structure

* fixed link in wsl setup

* fixed server link, added https cloning in yarn-setup

* removed package-lock.json

* added doc card, admonitions

* removed underline from nav buttons

docs/docs/developer/_category_.json

@@ -0,0 +1,4 @@
+{
+  "label": "Developer guide",
+  "position": 4
+}

docs/docs/developer/overview.mdx

@@ -0,0 +1,10 @@
+---
+title: Overview
+sidebar_position: 1
+sidebar_class_name: coming-soon
+sidebar_custom_props:
+  icon: TbArticle
+---
+
+
+Soon you'll be able to use our REST APIs to extend the app based on your needs.