VSCode integration with HLS

Added brief instructions to get started with VSCode.

I am not sure "integration" is the best wording, as it's more about getting VSCode + HLS extension to pick up correctly on a GHC installed from GHCup. Open to suggestions :)

changed the description

changed title from Adrien/adding VSCode integration to Adding VSCode integration

changed title from Adding VSCode integration to VSCode integration with HLS

Shouldn't it be enough to just link to https://marketplace.visualstudio.com/items?itemName=haskell.haskell so that we don't duplicate information?

I agree. The reason I went for more than a simple link is:

• their documentation mentioning GHCup simply points to GHCup's homepage, which is of no use for the user (okay, it's their problem but still, if we had a better page to give them, they could point there)
• their documentation mentioning HLS is quite an adventure: the user needs to follow a sequence of links throughout their documentation before they finally reach stack's documentation, which does provide system-ghc: true but in a different context (with no mention of GHCup of course).

As a maintainer I guess you need to balance between avoiding duplicating work and facilitating information to constitute useful (unfragmented) wholes (maintainers vs new users's conflicting interests I guess). The way I feel it, GHCup's point is to lower the barrier of entry to Haskell, so I think this would slightly favor new users.

If you are not convinced I can reduce this to a mention, as is done already for Vim integration. Your call.

merged