[Feature Request]: beam.apache.org search buries relevant links under ads

### What would you like to happen?

The search box on beam.apache.org just does a google search with `inurl:`. This seems effective, but unfortunately organic results are difficult to find under several ads. When I search for "dataframe" I see 4 ads and half of the actual result I'm looking for:


Also, in theory Google's index could be a bit out of date. We could provide a better experience by using a tool like https://lunrjs.com/, which can build an index of a static site and do queries on the client. There's a [hugo-lunr plugin](https://www.npmjs.com/package/hugo-lunr) we could leverage here.

### Issue Priority

Priority: 2

### Issue Component

Component: website