Print warnings when experimental features are used

[Gedochao]

Fixes #1281
Using experimental features will now cause Scala CLI to print an appropriate warning.
The warning can be suppressed with the --suppress-experimental-warning option or alternatively with the suppress-warning.experimental-features global config key.

▶ scala-cli config suppress-warning.experimental-features true

Directives:

▶ scala-cli --power -e '//> using publish.name "my-library"'
# The '//> publish.name "my-library"' directive is an experimental feature.
# Please bear in mind that non-ideal user experience should be expected.
# If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
# Compiling project (Scala 3.2.2, JVM)
# Compiled project (Scala 3.2.2, JVM)

Options:

▶ scala-cli --power -e 'println("Hello")' --markdown
# The '--markdown' option is an experimental feature.
# Please bear in mind that non-ideal user experience should be expected.
# If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
# Compiling project (Scala 3.2.2, JVM)
# Compiled project (Scala 3.2.2, JVM)
# Hello

Sub-commands:

▶ scala-cli --power export 
# The 'export' sub-command is an experimental feature.
# Please bear in mind that non-ideal user experience should be expected.
# If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at # https://github.com/VirtusLab/scala-cli
# Exporting to a sbt project...
# [error]  No inputs provided (expected files with .scala, .sc, .java or .md extensions, and / or directories).

Sub-commands' help:

▶ scala-cli --power publish -h
# Usage: scala-cli publish [options]
# Publishes build artifacts to Maven repositories.
# 
# You are currently viewing the basic help for the publish sub-command. You can view the full help by running: 
#    scala-cli --power publish --help-full
# For detailed documentation refer to our website: https://scala-cli.virtuslab.org/docs/commands/publishing/publish
# 
# The 'publish' sub-command is an experimental feature.
# Please bear in mind that non-ideal user experience should be expected.
# If you encounter any bugs or have feedback to share, make sure to reach out to the maintenance team at https://github.com/VirtusLab/scala-cli
# 
# Publishing options:
#   --organization string?                         Organization to publish artifacts under
# (...)

[lwronski]

LGTM