Automatic release update warnings. (#1336)

* Hide pretty help

* Automatic release update warnings.

* `httpie cli check-updates`

* adapt to the new loglevel construct

* Don't make the pie-colors the bold

* Apply review feedback.

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>

docs/README.md

@@ -1655,6 +1655,10 @@ If you’d like to silence warnings as well, use `-q` or `--quiet` twice:
 Let’s say that there is an API that returns the whole resource when it is updated, but you are only interested in the response headers to see the status code after an update:
 
 ```bash
+$ http --headers PATCH pie.dev/patch name='New Name'
+```
+
+Since you are only printing the HTTP headers here, the connection to the server is closed as soon as all the response headers have been received.
 Therefore, bandwidth and time isn’t wasted downloading the body which you don’t care about.
 The response headers are downloaded always, even if they are not part of the output
 
@@ -2400,6 +2404,14 @@ This command is currently in beta.
 "Program: http, Version: 0.0.1a0"
 ```
 
+#### `httpie cli plugins`
+
+`plugins` interface is a very simple plugin manager for installing, listing and uninstalling HTTPie plugins.
+
+In the past `pip` was used to install/uninstall plugins, but on some environments (e.g., brew installed
+packages) it wasn’t working properly. The new interface is a very simple overlay on top of `pip` to allow
+plugin installations on every installation method.
+
 By default, the plugins (and their missing dependencies) will be stored under the configuration directory,
 but this can be modified through `plugins_dir` variable on the config.