Add default configuration values to documentation

[rdcwaldrop1]

Relevant Document

https://tyk.io/docs/tyk-oss-gateway/configuration/

Describe the request

It would be really great to include the default values for the configuration options listed on this page. For example, I am curious if the default for TYK_GW_CLOSECONNECTIONS is true or false. Listing a default for each environment variable would be really helpful for configuration tuning and load testing scenarios.

Screenshots/Video

Maybe something like this?

Additional context

[letzya]

We do have "default:" for some fields but not for most of them. Thanks for the suggestion, We'll definitely improve this in all our config pages. FYI, the fix will be m in the repos of the actual projects since these pages are auto generated.