Use relative links in Markdown files

(also use “Note” alert style)

Author: jgarber623

README.md

@@ -32,7 +32,7 @@ gem "webmention"
 
 ## Usage
 
-See [USAGE.md](https://github.com/indieweb/webmention-client-ruby/blob/main/USAGE.md) for documentation of webmention-client-ruby's features.
+See [USAGE.md](USAGE.md) for documentation of webmention-client-ruby's features.
 
 ## Migrating to version 6
 

USAGE.md

@@ -1,6 +1,7 @@
 # Using webmention-client-ruby
 
-Before using webmention-client-ruby, please read the [Getting Started](https://github.com/indieweb/webmention-client-ruby/blob/main/README.md#getting-started) and [Installation](https://github.com/indieweb/webmention-client-ruby/blob/main/README.md#installation) sections of the project's [README.md](https://github.com/indieweb/webmention-client-ruby/blob/main/README.md).
+> [!NOTE]
+> Before using webmention-client-ruby, please read the [Getting Started](README.md#getting-started) and [Installation](README.md#installation) sections of the project's [README.md](README.md).
 
 ## Sending a webmention