Update to mermaid-isomorphic 3

Notably this updated to Mermaid 11 and adds an optional peer dependency
on `playwright`.

See
https://github.com/remcohaszing/mermaid-isomorphic/releases/tag/v3.0.0
for more details.

README.md

@@ -27,13 +27,14 @@ using [playwright](https://playwright.dev).
 ## Installation
 
 ```sh
-npm install remark-mermaidjs
+npm install rehype-mermaidjs
 ```
 
-In Node.js this package uses [playwright](https://playwright.dev) under the hood. To use it, you may
-need to install additional dependencies. These can be installed with:
+Outside of browsers `rehype-mermaidjs` uses [Playwright](https://playwright.dev). If you use this
+outside of a browser, you need to install Playwright and a Playwright browser.
 
 ```sh
+npm install playwright
 npx playwright install --with-deps chromium
 ```