Added table of contents to main readme file

README.md

@@ -4,6 +4,19 @@
 
 **Swagger Client** is a JavaScript module that allows you to fetch, resolve, and interact with Swagger/OpenAPI documents.
 
+## Table of Contents
+- [New](#new)
+- [Compatibility](#compatibility)
+- [Anonymized analytics](#anonymized-analytics)
+- [Documentation](#documentation)
+  - [Usage](#usage)
+  - [Development](#development)
+  - [Migrations](#migrations)
+- [Runtime](#runtime)
+  - [Node js](#nodejs)
+  - [Browsers](#browsers)
+- [Security Contact](#security-contact)
+
 ## New!
 
 **This is the new version of swagger-js, 3.x.** The new version supports Swagger 2.0 as well as OpenAPI 3.
@@ -68,9 +81,9 @@ Alternatively, you can set the environment variable `SCARF_ANALYTICS` to `false`
 - [Migration guide](docs/migration/migration-2-x-to-3-x.md)
 - [Graveyard](docs/migration/graveyard-3-x.md)
 
-### Runtime 
+## Runtime 
 
-### Node.js
+#### Node.js
 
 `swagger-client` requires Node.js `>=12.20.0` and uses different `fetch` implementation depending
 on Node.js version.
@@ -81,7 +94,7 @@ on Node.js version.
 > NOTE: swagger-client minimum Node.js runtime version aligns with [Node.js Releases](https://nodejs.org/en/about/releases/)
 > which means that we can drop support for **EOL** (End Of Life) Node.js versions without doing major version bump.
 
-### Browsers
+#### Browsers
 
 `swagger-client` works in the latest versions of Chrome, Safari, Firefox, and Edge
 and uses [native fetch](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) implementation