Update schema.md

add block_number to token schema

Author: ezioruan

docs/schema.md

@@ -116,6 +116,7 @@ symbol                       | string      |
 name                         | string      |
 decimals                     | bigint      |
 total_supply                 | numeric     |
+block_number                 | bigint     |
 
 ---
 
@@ -155,4 +156,4 @@ trace_id                     | string      |
 You can find column descriptions in [https://github.com/medvedev1088/ethereum-etl-airflow](https://github.com/medvedev1088/ethereum-etl-airflow/tree/master/dags/resources/stages/raw/schemas)
 
 Note: for the `address` type all hex characters are lower-cased.
-`boolean` type can have 2 values: `True` or `False`.
+`boolean` type can have 2 values: `True` or `False`.