docs need a note that built-in wrap plugins work with "each", not "all"

When attempting to override a global specified in the jest.config.js we've found it isn't overriden.

We have a set of globals which are basically stubs (in jest.config.js) e.g.

module.exports = {
    globals: {
        YJ: {
            i18n: {
                react: {}
            }
        }
    },
    ...

Then when using jest-wrap to override the i18n key in that global we attempt to do:

const mockYJ = () => ({
    i18n: {
        old_components: {
            form: "1234"
        }
    }
});

wrap()
    .withGlobal("YJ", () => mockYJ)
    .describe("Forms tests", function() {
        beforeAll(function() {
            console.log(YJ.i18n); // { react: {} } 
			// expected { i18n: { old_components: { form: "1234" } } }

But using beforeEach works as expected

wrap()
    .withGlobal("YJ", () => mockYJ)
    .describe("Forms tests", function() {
        beforeEach(function() {
            console.log(YJ.i18n); // { i18n: { old_components: { form: "1234" } } }