Explain index as key can be ok

The pitfall warning on https://beta.reactjs.org/learn/rendering-lists states that using index or random for keys is bad. However, this is the only mention of using indexes of keys. I think it should state that using indexes is bad, but it should also be clear that using random values much worse.

The problem is using index as key is a well known anti-pattern in the React world. People come up with much worse solutions, e.g. use a random key, to get rid of ESLint warnings.

Also there are legitimate use cases for an index as a key, for example when rendering a static list of data. I think this should be acknowledged in the Where to get your key section.

Abre la página Rendering Lists en https://beta.reactjs.org/learn/rendering-lists y lee la advertencia sobre los errores comunes y la sección “Where to get your key”. Actualiza la explicación para que distinga entre las keys de índice y las keys aleatorias, y reconozca las listas estáticas como un caso legítimo para usar keys de índice; se considerará terminado cuando la guía sea clara y coherente en ambos lugares.