Set all headings to inherit the parent font size and reset the font
weight to normal. This prevents you from accidentally using browser
default sizes in your designs and deviating from your design system.
The only reason the config() helper function existed was to access your design tokens in your CSS, like:
```css
.foo {
color: config('colors.blue')
}
```
Now that design tokens are nested in the new `theme` section, using the `config()` function is a bit more verbose:
```css
.foo {
color: config('theme.colors.blue')
}
```
This PR removes the `config()` function in favor of a new `theme()` function that is already scoped to the `theme` section of the config:
```css
.foo {
color: theme('colors.blue')
}
```
I can't think of any reason at all why you would need to access the non-theme values in your config from your CSS (like enabled variants, or your list of plugins), and the word `theme` is much more expressive than `config`, so I think this is a worthwhile change.
Instead of plugins being configured directly, they grab their configuration from the Tailwind config passed to them. This makes core plugins consistent with how we will recommend third-party plugins be authored so that the configuration for everything in the system is readable through the theme.
Not 100% convinced this is a net positive change, but I regret not having done things this way at the beginning.
In 0.x, we pass the `separator` and `className` values already escaped, so `:` comes through as `\:` for example, and `w-1/2` comes through as `w-1\/2`.
At first this sounds fine, less work for the plugin author right? But CSS escaping rules are kind of complicated and you have to escape characters differently depending on whether or not they are at the start of an identifier.
For example, it's totally fine for a class to contain a zero (`0` ), but it can't _start_ with a zero. For a class to start with a zero, it needs to be escaped like this: `\30 `
This means that as a general rule, trying to escape the individual segments of a class separately is a bad idea — you should escape the class as a whole so only the necessary escaping is applied. We break this rule when we pre-escape the separator and className for plugin authors who use the `modifySelectors` function.
We already require users to manually escape class names when they are using `addUtilities` or `addComponents`, so to me it feels more consistent for things to work this way and it's how they should have worked from day one.
Basically this code:
```js
function({ addVariant }) {
addVariant('first-child', ({ modifySelectors, separator }) => {
modifySelectors(({ className }) => {
return `.first-child${separator}${className}:first-child`
})
})
},
```
...would need to be re-written like this if I merge this change:
```js
function({ addVariant, e }) {
addVariant('first-child', ({ modifySelectors, separator }) => {
modifySelectors(({ className }) => {
return `.${e(`first-child${separator}${className}`)}:first-child`
})
})
},
```
Although I think this is the right way for this to work, I hesitate because it's a breaking change that makes any variant plugins authored for 0.x incompatible with 1.x. It's an easy fix on the plugin author's part, but it's still annoying.
I'm leaning towards merging so I don't regret this even more later when the plugin ecosystem is a lot bigger. Anyone have any thoughts?
