I have made some changes related to spelling and use of Spanish.
I hope it helps.
* [x] I have read [freeCodeCamp's contribution guidelines](https://github.com/freeCodeCamp/freeCodeCamp/blob/master/CONTRIBUTING.md).
* [x] My pull request has a descriptive title (not a vague title like `Update index.md`)
* [x] My pull request targets the `master` branch of freeCodeCamp.
* [x] None of my changes are plagiarized from another source without proper attribution.
* [x] My article does not contain shortened URLs or affiliate links.
* Added article Material Design
* Spanish translation of Material Design article.
* Added article User interface design
* Spanish translation of User interface design.
* Fixed more information and courses of the article material design (guide english and spanish)
* Fixed more information and courses of the article user interface design (guide english and spanish)
* Fixed localTitle of the article material design (guide spanish)
* Fixed localTitle of the article user interface design (guide spanish)
* fix/suggested-changes
* fix/suggested-changes
