Missing documentation on how to escape special characters in http_access_log.pattern

[darksoul96]

Description:
The documentation in [1] explains how to set up different attributes in http_access_log.pattern in deployment.toml configuration.
However, it lacks explanation on how to escape certain special character.

Suggested Solution:
Update documentation on how to escape special characters when having custom log patterns.

[1] https://is.docs.wso2.com/en/latest/deploy/monitor/http-access-logging/