docs: add query syntax rules for garf-bid-manager

Author: AndreyMarkinPPC

docs/fetchers/bid-manager.md

@@ -1,5 +1,8 @@
 ## garf for Bid Manager API
 
+[![PyPI](https://img.shields.io/pypi/v/garf-bid-manager?logo=pypi&logoColor=white&style=flat-square)](https://pypi.org/project/garf-bid-manager)
+[![Downloads PyPI](https://img.shields.io/pypi/dw/garf-bid-manager?logo=pypi)](https://pypi.org/project/garf-bid-manager/)
+
 Interacts with [Bid Manager API](https://developers.google.com/bid-manager).
 
 ## Install
@@ -74,3 +77,13 @@ csv_writer.write(fetched_report, 'query')
 | name | values| comments |
 |----- | ----- | -------- |
 | `credentials_file`   | File with Oauth or service account credentials | You can expose `credentials_file` as `GARF_BID_MANAGER_CREDENTIALS_FILE` ENV variable|
+
+## Query syntax
+
+`garf-bid-manager` uses simplified syntax for writing queries.
+
+|area | Bid Manager | garf|
+| --- |----- | ----- |
+| filters and metrics case | upper (FILTER_ADVERTISER)| any (filter_advertiser) |
+| prefix| mandatory (FILTER_ADVERTISER)| optional for filters (advertiser) |
+| resource case | upper (STANDARD)| any (standard) |

docs/fetchers/merchant-center-api.md

@@ -1,5 +1,8 @@
 # garf for Merchant Center API
 
+[![PyPI](https://img.shields.io/pypi/v/garf-merchant-api?logo=pypi&logoColor=white&style=flat-square)](https://pypi.org/project/garf-merchant-api)
+[![Downloads PyPI](https://img.shields.io/pypi/dw/garf-merchant-api?logo=pypi)](https://pypi.org/project/garf-merchant-api/)
+
 ## Install
 
 Install `garf-merchant-api` library

docs/fetchers/youtube-data-api.md

@@ -1,5 +1,8 @@
 # garf for YouTube Data API
 
+[![PyPI](https://img.shields.io/pypi/v/garf-youtube-data-api?logo=pypi&logoColor=white&style=flat-square)](https://pypi.org/project/garf-youtube-data-api)
+[![Downloads PyPI](https://img.shields.io/pypi/dw/garf-youtube-data-api?logo=pypi)](https://pypi.org/project/garf-youtube-data-api/)
+
 Interacts with [YouTube Data API](https://developers.google.com/youtube/v3/docs).
 
 ## Install

docs/fetchers/youtube-reporting-api.md

@@ -1,5 +1,8 @@
 # garf for YouTube Data API
 
+[![PyPI](https://img.shields.io/pypi/v/garf-youtube-reporting-api?logo=pypi&logoColor=white&style=flat-square)](https://pypi.org/project/garf-youtube-reporting-api)
+[![Downloads PyPI](https://img.shields.io/pypi/dw/garf-youtube-reporting-api?logo=pypi)](https://pypi.org/project/garf-youtube-reporting-api/)
+
 ## Install
 
 Install `garf-youtube-reporting-api` library