Generalize the adding bootstrap documentation

[jquense]

Picking a particular react bootstrap library feels like too strong of an opinion for supplementary CRA docs. I trimmed it down to point out the two most popular options and remove library specific documentation to focus on the bits that are more CRA specific, e.g. using sass files.

[iansu]

There's also this PR that adds a section on installing plain bootstrap, in addition to reactstrap: #5565

[Timer]

We definitely don't want to advocate jQuery usage. I'd be OK with advocating something like "Bootstrap for styling only", where you use just CSS and no JS.

[jquense]

I think (at least it was my intention that) the copy I've added above here covers the "don't use jquery" aspect, with "here are the two main alternatives to that" but not trying to recommend one particular solution. w/d/t @Timer ?

[guledali]

@jquense I actually like yours more than the reactstrap, that's because you have included an guide on how to theme which I think is really important using component library like react + a lot people are base their design system on bootstrap so the ability to easily customize the components is a win for me.

Example

bootstrapUtils.addStyle(Button, 'custom');

const customButtonStyle = (
  <div>
    <style type="text/css">
      {`
    .btn-custom {
        background-color: purple;
        color: white;
    }
    `}
    </style>
    <Button bsStyle="custom">Custom</Button>
  </div>
);

render(customButtonStyle);

What I don't like though is that your readme.md kinda looks messy to me, and I think it has to do with you maintaining two different bootstrap versions 3 and 4.
I wish your readme.md was as clean as the overall site https://react-bootstrap.netlify.com/

I made an issue on this check the react-bootstrap/react-bootstrap#3359

[jquense]

anything I can do here?

[iansu]

The end of this sentence doesn't sound right. expense of less featues sounds kind of like a double negative. Maybe something like at the expense of some features?

[iansu]

Our default template uses semicolons.

[iansu]

Add semicolon back.

[iansu]

I think this is a good change. However, I agree with @Timer that it might be good to mention that just installing the bootstrap CSS is a valid option for theming only with no JS features (like dropdowns, etc).

[stale]

This pull request has been automatically marked as stale because it has not had any recent activity. It will be closed in 5 days if no further activity occurs.

[iansu]

Thanks!