feat(docs): added new learn section for the website (#1041)

I'm review the way Wing information is laid out. This is the initial move of some information

-  Removed "API" in the header
- Learn now goes to the new page inspired by (https://www.rust-lang.org/learn)

The new learn page consists of material to help folks learn Wing, either by hands on examples, or docs (e.g standard lib) or diving into some core concepts of Wing.

Next phase will be to tidy up the other pages and flow, then write the "Wing Book" (inspired by https://guide.sst.dev/ and https://doc.rust-lang.org/book/) which will teach people Wing and it's fundamentals through practical examples and hands up walkthroughs.

Preview of the new pages
- https://wing-docs-git-new-learn-section-for-website-monada.vercel.app/learn-wing (learn page)
- https://wing-docs-git-new-learn-section-for-website-monada.vercel.app/install (install page)

docusaurus.config.js

@@ -284,26 +284,19 @@ const config = {
         },
         items: [
           {
-            to: "docs",
+            to: "install",
             position: "left",
-            label: "Getting started",
+            label: "Install",
             className: "header-text-link",
             target: "_self",
           },
           {
-            to: "docs/learn",
+            to: "learn-wing",
             position: "left",
             label: "Learn",
             className: "header-text-link",
             target: "_self",
           },
-          {
-            to: "docs/api",
-            position: "left",
-            label: "API",
-            className: "header-text-link",
-            target: "_self",
-          },
           {
             to: "docs/libraries",
             position: "left",