docs: fix typos (#327)

admin/extending-remarkable.md

@@ -32,7 +32,7 @@ A block token is a bit more complex. It may wrap one or more tokens, and can spa
 
 The plain markdown text above would be parsed into three tokens:
 
-- `heading_open`: Marks the begining of the heading. May have additional props, such as `hLevel: 3` (heading level) in this case.
+- `heading_open`: Marks the beginning of the heading. May have additional props, such as `hLevel: 3` (heading level) in this case.
 - `text`: Plain text token, with a value of "Hi there".
 - `heading_close`: Marks the end of the heading. In this case, it would also have a `hLevel: 3` prop.
 

admin/local-third-party-project-testing.md

@@ -1,6 +1,6 @@
 Sometimes you want to test the latest version of Docusaurus on a third-party project via `npm` or `yarn` without having to publish it to npm itself. For example, you may want to use the latest code in `master`.
 
-> If you want to use Docusaurus to test Docusuarus, see the [testing changins on Docusaurus itself doc](./testing-changes-on-Docusaurus-itself.md)
+> If you want to use Docusaurus to test Docusaurus, see the [testing changes on Docusaurus itself doc](./testing-changes-on-Docusaurus-itself.md)
 
 There are two reasonable ways to use a local version of the Docusaurus npm package to test changes you make to the Docusaurus core on a third-party project.
 

admin/testing-changes-on-Docusaurus-itself.md

@@ -1,4 +1,4 @@
-If you are developing the Docusuarus core and you want a quick way to test your changes, you can use the Docusaurus website itself as your testing area.
+If you are developing the Docusaurus core and you want a quick way to test your changes, you can use the Docusaurus website itself as your testing area.
 
 > For tips on testing other projects, see the [local testing of third-party projects doc](./local-third-party-project-testing.md).