Make some minor updates to the libraries input documentation

This makes some small corrections and improvements to the existing documentation for the action's libraries input.

Author: per1234

README.md

@@ -50,7 +50,7 @@ Keys:
 
 Keys:
 - `source-url` - download URL for the archive (e.g., `https://github.com/arduino-libraries/Servo/archive/master.zip`).
-- `source-path` - path to install as a library. Paths are relative to the root folder of the archive. If the archive doesn't have a root folder, use `..` as `source-path` to install from the archive root. The default is to install from the root folder of the archive.
+- `source-path` - path to install as a library. Paths are relative to the root folder of the archive, or the root of the archive if it has no root folder. The default is to install from the root folder of the archive.
 - `destination-name` - folder name to install the library to. By default, the folder will be named according to the source archive or subfolder name.
 
 ### `sketch-paths`

compilesketches/compilesketches.py

@@ -48,7 +48,7 @@ class CompileSketches:
     cli_version -- version of the Arduino CLI to use
     fqbn_arg -- fully qualified board name of the board to compile for. Space separated list with Boards Manager URL if
                 needed
-    libraries -- space-separated list of libraries to install
+    libraries -- YAML-format or space-separated list of libraries to install
     sketch_paths -- space-separated list of paths containing sketches to compile. These paths will be searched
                     recursively for sketches.
     verbose -- set to "true" for verbose output ("true", "false")
@@ -242,7 +242,7 @@ def sort_dependency_list(self, dependency_list):
                         # All other URLs are assumed to be downloads
                         sorted_dependencies.download.append(dependency)
                 elif self.dependency_source_path_key in dependency:
-                    # Libraries with source-path and no source-url are assumed to be paths
+                    # Dependencies with source-path and no source-url are assumed to be paths
                     sorted_dependencies.path.append(dependency)
                 else:
                     # All others are Library/Board Manager names
@@ -285,7 +285,9 @@ def install_platforms_from_board_manager(self, platform_list, additional_url_lis
         self.run_arduino_cli_command(command=core_install_command, enable_output=self.get_run_command_output_level())
 
     def get_manager_dependency_name(self, dependency):
-        """Return the appropriate name value for a repository dependency
+        """Return the appropriate name value for a manager dependency. This allows the NAME@VERSION syntax to be used
+        with the special "latest" ref for the sake of consistency (though the documented approach is to use the version
+        key to specify version.
 
         Keyword arguments:
         dependency -- dictionary defining the Library/Board Manger dependency