Improve README

Improve the README text.

Signed-off-by: Teodora Sechkova <[email protected]>

Author: sechkova

tuf/ngclient/README.md

@@ -7,16 +7,16 @@ described in the TUF specification (see
 https://theupdateframework.github.io/specification/latest/#detailed-client-workflow)
 
 **tuf.ngclient.FetcherInterface** is an abstract class that client
-implementers can optionally use to integrate with their own
-network/download infrastructure -- a Requests-based implementation is
+implementers can implement a concrete class of in order to reuse their
+own networking/download libraries -- a Requests-based implementation is
 used by default.
 
 This package:
 * Aims to be a clean, easy-to-validate reference client implementation
   written in modern Python
-* At the same time aims to be the library choice for anyone
+* At the same time aims to be the library of choice for anyone
   implementing a TUF client in Python: light-weight, easy to integrate
   and with minimal required dependencies
-* Is still under development but planned to become the default client
-  in this code base (as in the older tuf.client will be deprecated in
-  the future)
+* Is still under development but is planned to become the default client
+  in this implementation (i.e., the older `tuf.client` will be deprecated
+  in the future)