docs: Create FEATURES.md to doc features and todos (#1309)

FEATURES.md

@@ -0,0 +1,23 @@
+**Robotoff** is a service managing potential Open Food Facts updates (also known as _insights_) and predictions (which can then be combined to generate an insight).
+These insights include a growing set of facts, including:
+
+### Insights 
+- the product category, weight, brand, packager codes and expiration date
+- some of its labels
+- abusive pictures (selfies)
+- rotated pictures
+- EXPAND ME (Auto-select…)
+
+### Insights applied automatically
+
+- EXPAND ME
+
+### API Features/Routes
+- Fetch insights
+- Annotate an insight (accept or reject)
+
+### TODO
+- Regenerate category insights
+- Regenerate image insights
+
+A detailed description of [how predictions and insights work is available here](https://openfoodfacts.github.io/robotoff/explanations/predictions/).