Update format of library.properties documentation link

A change to the way the arduino/arduino-cli repository's documentation is published results in links that don't specify the version via the URL providing increasingly outdated content.

The new link will always point the the documentation associated with the latest release of Arduino CLI.

Author: per1234

README.md

@@ -78,7 +78,7 @@ Note: the original space-separated list format is also supported. When this synt
 ##### Library Manager
 
 Keys:
-- `name` - name of the library, as defined in the `name` field of its [library.properties](https://arduino.github.io/arduino-cli/library-specification/#libraryproperties-file-format) metadata file. The library will be installed to a folder matching the name, but with any spaces replaced by `_`.
+- `name` - name of the library, as defined in the `name` field of its [library.properties](https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format) metadata file. The library will be installed to a folder matching the name, but with any spaces replaced by `_`.
 - `version` - version of the library to install. Default is the latest version.
 
 ##### Local path