message: docs: Fix a couple typos and a link in README.md
diff: - Integrate API Introduction into side menu - ReDoc takes advantage of markdown headings from OpenAPI description field. It pulls them into side menu and also supports deep linking.
  - High-level grouping in side-menu via [`x-tagGroups`](docs/redoc-vendor-extensions.md#x-tagGroups) vendor extension
  - Simple integration with `create-react-app` ([sample](https://github.com/APIs-guru/create-react-app-redoc))
  -- Branding/cusomizations via [`theme` option](#redoc-options-object)
  +- Branding/customizations via [`theme` option](#redoc-options-object)
  ## Roadmap
  - [x] ~~[OpenAPI v3.0 support](https://github.com/Rebilly/ReDoc/issues/312)~~
  @@ -103,7 +103,7 @@ Additionally, all the 1.x releases are hosted on our GitHub Pages-based **CDN**:
  ```
  That's all folks!
  -**IMPORTANT NOTE:** if you work with untrusted user spec, use `untrusted-spec` [option](#redoc-tag-attributes) to prevent XSS security risks.
  +**IMPORTANT NOTE:** if you work with untrusted user spec, use `untrusted-spec` [option](#redoc-options-object) to prevent XSS security risks.
  ### 1. Install ReDoc (skip this step for CDN)
  Install using [yarn](https://yarnpkg.com):
  @@ -189,7 +189,7 @@ ReDoc makes use of the following [vendor extensions](http://swagger.io/specifica
  * [`x-ignoredHeaderParameters`](docs/redoc-vendor-extensions.md#x-ignoredHeaderParameters) - ability to specify header parameter names to ignore
  ### `<redoc>` options object
  -You can use all of the following optins with standalone version on <redoc> tag by kebab-casing them, e.g. `scrollYOffset` becomes `scroll-y-offset` and `expandResponses` becomes `expand-responses`.
  +You can use all of the following options with standalone version on <redoc> tag by kebab-casing them, e.g. `scrollYOffset` becomes `scroll-y-offset` and `expandResponses` becomes `expand-responses`.
  * `untrustedSpec` - if set, the spec is considered untrusted and all HTML/markdown is sanitized to prevent XSS. **Disabled by default** for performance reasons. **Enable this option if you work with untrusted user data!**
  * `scrollYOffset` - If set, specifies a vertical scroll-offset. This is often useful when there are fixed positioned elements at the top of the page, such as navbars, headers etc;
  