fix(@cypress/webpack-batteries-included-preprocessor): Ensure typescript options are set if typescript path is provided

[chrisbreiding]

• Closes Can't run Typescript tests in Cypress when I have @cypress/webpack-batteries-included-preprocessor enabled #15767

User Facing Changelog

N/A - this only affects the @cypress/webpack-batteries-included-preprocessor package

Details

• Fixes an issue with @cypress/webpack-batteries-included-preprocessor where passing in webpackOptions (namely via the defaultOptions) and the typescript path would not added the needed typescript-related webpack options.
• Updates the README to note that passing in the typescript path is necessary to enable TypeScript support

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[cypress]

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Test summary

200 • 0 • 1 • 0 • 0

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Run details

Project	cypress
Status	Passed
Commit	0788219
Started	Apr 13, 2021 9:35 PM
Ended	Apr 13, 2021 9:43 PM
Duration	08:17 💡
OS	Linux Debian - 10.8
Browser	Chrome 89

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[chrisbreiding]

Closing in favor of #15991, so it's against master