[FEATURE] Update local.md

[owolabioromidayo]

Is your feature request related to a problem? Please describe.

I had 2 minor issues setting up this project on Linux.
They could have been easily prevented if more information was contained in https://github.com/hotosm/raw-data-api/blob/develop/docs/src/installation/local.md.

Describe the solution you'd like

If it is useful, I would like to update the installation/local.md file with instructions to:

1. Setup postgis on the target database (to prevent this error)
   

2. Prevent this error if it occurs

AttributeError: module 'eventlet.green.select' has no attribute 'epoll'  

Describe alternatives you've considered

We could just leave the file as it is.

Additional context

None.

[kshitijrajsharma]

Thanks for the issue it does mention enable postgis extension in configuration https://github.com/hotosm/raw-data-api/blob/develop/docs/src/installation/configurations.md if it helps . Feel free to revise installation docs to make it more clear

[owolabioromidayo]

I guess the issue was it wasn't referenced in local.md.
I have added the postgis setup instructions anyways, will reference the configurations.md file in it.

[owolabioromidayo]

Done here. 8ca3de3