Updated harvester submodule

Added known issues and license to README

README.md

@@ -140,14 +140,9 @@ explorer-specific format. It exposes a GraphQL endpoint and enables subscription
 the Explorer API and the Substrate node. Its design is based on flat [Material](https://material.angular.io/) component 
 design, styled in Polkascan branding.
 
+## Modifications
 
-
-
-
-
-# Modifications
-
-## Substrate Node
+### Substrate Node
 By default, a build of [Substrate Node Template](https://github.com/substrate-developer-hub/substrate-node-template) is 
 used. If a local Substrate node is already running on the host machine, you can change
 environment variable in the [docker-compose.yml](https://github.com/polkascan/explorer/blob/main/docker-compose.yml#L15):
@@ -157,9 +152,9 @@ Or to any public or private websocket endpoint
 
 To use PolkadotJS Apps with the local Substrate node, go to https://polkadot.js.org/apps/?rpc=ws%3A%2F%2F127.0.0.1%3A9944#/explorer
 
-## Explorer UI 
+### Explorer UI 
 
-### Datasources
+#### Datasources
 
 The UI is utilizing [PolkAdapt](https://github.com/polkascan/polkadapt) to combine on-chain data retrieved directly from the Substrate node, with the GraphQL endpoint with indexed data served by the [Explorer API](https://github.com/polkascan/explorer-api). In this way data like events and extrinsics can be retrieved fast, with the verification of on-chain data.
 
@@ -178,3 +173,12 @@ By default, the UI are using the local endpoints, new networks can be added by e
   }
 }
 ```
+
+## Known Issues and Limitations
+
+* Substrate runtimes that implements metadata prior to `MetadataV14` decode in a different format as expected by the explorer, so not all functionality is available. This can have effect on early blocks as well, a workaround is to set `BLOCK_START` env setting for the harvester, to a block number with `MetadataV14`.
+* Errors during building `explorer-ui` Docker container on M1 architecture. This could happen when the chromium binary is not available for arm64, there is [a workaround available](https://github.com/polkascan/explorer-ui/issues/26)
+* Currently, the `explorer-api` application supports Python version >3.6 and <3.10 
+
+## License
+https://github.com/polkascan/explorer/blob/main/LICENSE