Add descritption of tolerance in dataschema page

Author: mirkomanset

md-docs/user_guide/data_schema.md

@@ -18,6 +18,7 @@ A Column object has some mandatory attributes and others that depends on its rol
 | Subrole | Additional specification of the role in the Task. Some entities belong to the same Role but have different meanings, the Subroles allows to distinguish between them. More information in the following sections. | Depends on Task Type |
 | Is Nullable | If the entity allows missing values. | Mandatory |
 | Dims | List with the number of elements each dimension of the array has. The value -1 indicates that that dimension can have an arbitrary number of elements. | Required when Data Type is Array |
+| Tolerance | Specifies the tolerance for image data, defining the acceptable pixel variation in image size. <ul><li>Tol=0: Strict matching, only images of the exact specified size are accepted.</li><li>Tol > 0: Allows a size variation of up to ±Tol pixels in each dimension. For example, if the expected size is (100, 100) and Tol = 5, images between (95, 95) and (105, 105) are accepted.</li><li>Tol=none: Fully flexible, images of any size are allowed.</li></ul> | Required when Column Role is Input and Data Structure is Image. |
 | Possible values | List of values the categorical variable can assume. They can be either strings or numbers. When Task Type is Classification Multilabel and Role is Target, possibile values must be \[0, 1\] indicating the presence or not of that class. | Mandatory when Column Data Type is Categorical |
 | Classes Names | Names of the classes in the Task. The length of this list must match the length of the Dims of the array. | Required when Column Role is Target and Task Type is Classification Multilabel.|
 |Image Mode| Type of image, it can be RGB, RGBA, GRAYSCALE. It also determines the Data Type, which is Array 3 for RBG and RGBA and Array 2 for GRAYSCALE. | Required when Column Role is Input and Data Structure is Image.|