Update README.md

[i-herrera]

For tutorials:

• I double checked the wiring in the schematics/images
• I exported the cover image without background
• I used SVG format for pure vector images
• I updated the metadata.json file of the tutorial
• I updated the metadata.json file of the previous tutorial to contain the "next" link
• I did a spell checking before requesting a review
• I used title case for titles