Some content change suggestions

[ThomasG77]

No big rewrite, just some feedback. If OK, will make changes and a corresponding PR

Replace "The two most popular JavaScript libraries for use with OSM tiles are: " with "The three most popular JavaScript libraries for use with OSM tiles are: "

https://github.com/switch2osm/switch2osm.github.io/blob/70944887bd6cffa27581baf02e1b20859ef5e651/the-basics/index.md#L30

Then, add after

https://github.com/switch2osm/switch2osm.github.io/blob/70944887bd6cffa27581baf02e1b20859ef5e651/the-basics/index.md#L30-L34

 * Mapbox GL JS – use WebGL for performances, mainly for vector tiles

Remove (outdated) the following content

https://github.com/switch2osm/switch2osm.github.io/blob/70944887bd6cffa27581baf02e1b20859ef5e651/the-basics/index.md#L35-L37

Metrics need update (to 300GB+ of fast storage, 24GB of memory, and a quad-core processor for the entire planet. part in particular) in the following

https://github.com/switch2osm/switch2osm.github.io/blob/70944887bd6cffa27581baf02e1b20859ef5e651/serving-tiles/index.md#L24

Remove the broken link or point to https://www.interline.io/osm/extracts/ (need a subscription so not really fond to keep it https://app.interline.io/products/osm_extracts/orders/new)

https://github.com/switch2osm/switch2osm.github.io/blob/70944887bd6cffa27581baf02e1b20859ef5e651/serving-tiles/index.md#L29

[SomeoneElseOSM]

I think the "the basics" page needs more changes than described above - I'd suggest some sort of introduction of vector vs raster tiles first, followed by redirecting the user to something else based on what they want. Most of the "the basics" page still stands as an introduction to raster tiles, but it shouldn't claim to be "how most people do things". Unfortunately, I'm struggling to find a vector tile option that isn't (a) a closed ecosystem, (b) an unfinished and unmaintained hobby project or (c) dead.

Richard's raised #63 , and has far more experience in that area than me - I'll try and add some "what I'd like to see as a punter" comments to that. Once we've got an acknowledgement that vector tiles are a thing, I think it makes sense to change "the basics" to link to either there or to this "raster tile basics" content.