Add link to docs page on how to install the Python extension to README

[JetForMe]

Environment data

• VS Code version: 1.52.1
• OS and version: macOS Catalina

I've got an existing python flask project, which I run from the command line on macOS using flask run. I'd like to use VS Code, so I tried code ., which opens it up. But instructions online said to install the python extension to VS Code, and links me here.

That page says "Step 2. Install the Python extension for Visual Studio Code." but doesn't say how. It took me forever to look in the banner area to notice the Install button. Add "by clicking the Install button above" to make this clearer.

[brettcannon]

I think we could link to https://code.visualstudio.com/docs/editor/extension-gallery in the README, but I would rather not tie our README to the Marketplace's UI as that could change without us knowing.

[luabud]

Hey @JetForMe, thanks for your suggestion! The problem is that our README also shows on our GitHub repo, so "by clicking on the Install button above" wouldn't make sense there, as there isn't such a button. I like Brett's suggestion about linking to the documentation, so something like:

Step 2. Install the Python extension for Visual Studio Code.

Or we can link it directly to the Extension Marketplace docs. I just felt some poeple could be confused as to why they were directed to a doc titled "Extension Marketplace" when they just wanted to install the Python extension.

[JetForMe]

Makes sense. Thanks!

[brettcannon]

@JetForMe BTW if you're up for doing a PR for this we would happily review it.