Add the README.md as the default package documentation for libraries

[TharmiganK]

Description

With update 11, the default package documentation has changed to README.md file[1]. This change is backward compatible. But still there is an error printed for the libraries which has Package.md/Module.md files:

WARNING [log] The default file for package documentation is changed to README.md. If you prefer to use the Package.md, add the following line under the '[package]' section in your Ballerina.toml file:
        readme = "Package.md"

[1] ballerina-platform/ballerina-spec#1256

As a solution the Package.md/Module.md files should be replaced by a README.md file. This has to be done for all the libraries

• io
• java.arrays
• math.vector
• time
• url
• avro
• constraint
• crypto
• log
• os
• persist
• protobuf
• random
• task
• xslt
• cache
• data.xmldata
• data.yaml
• file
• ftp
• ldap
• mime
• tcp
• udp
• uuid
• auth
• data.csv
• data.jsondata
• edi
• email
• jwt
• mqtt
• oauth2
• toml
• yaml
• http
• grpc
• soap
• transaction
• websocket
• websub
• websubhub
• graphql
• sql

Version

Ballerina SwanLake Update 11

[NipunaRanasinghe]

Need to do the same change for all the ballerinax modules (connectors) as well.