docs: various doc improvements (#9396)

See commits for details.

Closes #1837, #5880, #7822, #8101, #8821, #9367, #9382, #9378, #4731

docs/api/puppeteer.page.emulatevisiondeficiency.md

@@ -29,7 +29,7 @@ Promise<void>
 ## Example
 
 ```ts
-const puppeteer = require('puppeteer');
+import puppeteer from 'puppeteer';
 
 (async () => {
   const browser = await puppeteer.launch();