[IMP] contract_variable_quantity: pre-commit auto fixes

contract_variable_quantity/readme/CONFIGURE.md

@@ -0,0 +1,18 @@
+1.  Go to Invoicing \> Configuration \> Contracts \> Formulas
+    (quantity).
+
+2.  Define any formula based on Python code that stores at some moment a
+    float/integer value of the quantity to invoice in the variable
+    'result'.
+
+    You can use these variables to compute your formula:
+
+    - *env*: Environment variable for getting other models.
+    - *context*: Current context dictionary.
+    - *user*: Current user.
+    - *line*: Contract recurring invoice line that triggers this
+      formula.
+    - *contract*: Contract whose line belongs to.
+    - *invoice*: Invoice (header) being created.
+
+![](images/formula_form.png)