Add README for scales data

src/data/README.MD

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+## Intro
+Climbing scales are defined in the '.csv' files within this folder.
+
+Each discipline have dedicated files:
+ - [aid](./aid.csv) climbing
+ - [bouldering](./boulder.csv)
+ - [ice](./ice.csv) climbing
+ - [sport/trad](./routes.csv) climbing
+
+In each file is defined a *score* representing a discrete virtual grade starting from 0.
+For each score it is reported the correspective grade for each supported scale.
+A grade in a given scale (e.g. french 6a) can corrispond to multiple scores.
+
+## Adding/Editing scales
+
+The main step to add or modify a scale is to add or modify the correspective column in the desired csv file.
+
+Scales are converted into json files with [this](./csvtojson.ts) script (see instruction within the script).