Recipe - Blocking metrics and indices, teleconnections and weather regimes (MiLES)

Issue to implement [Blocking metrics and indices, teleconnections and weather regimes (MiLES) recipe](https://docs.esmvaltool.org/en/latest/recipes/recipe_miles.html) in CMEW.

Variables needed: `zg` (Geopotential height at 500 hPa) from ERA-Interim reanalysis data.

Note: ERA5 and ERA Interim provides Geopotential (which needs to be divided by 9.8 m/s^2 to convert to Geopotential height) but the recipe does a check on the range of values provided and does a conversion to geopotential height inside the codes.

Start by reading the linked MiLES recipe and then locate how CMEW integrates ESMValTool recipes. Trace the required ERA-Interim zg input and the recipe's geopotential-to-geopotential-height conversion and range check. Done means the recipe is implemented in CMEW and can run with the documented variable and data source.

Written by the indexing model from the issue text.