add a kasm blurb that can be used on all KasmVNC based images

[thelamer]

This can be setup to add information after the app setup block using the following variables:

# kasm variables
kasm_blurb: true
external_http_port: "3000"
external_https_port: "3001"
noto_fonts: "font-noto-cjk"
show_nvidia: true

If only the kasm_blurb: true is set all defaults will be set as laid out here minus the nvidia support that needs to be specifically enabled for images that support it as Alpine does not. The Alpine blurb in the Nvidia section is to cover us for webtop or other images that may be multi distro base in the future.

The ports are needed for images that are off the default 3000 and 3001, the maintainer will need to know what font noto package to use for their image base flavor here are the current packages:

Arch: noto-fonts-cjk
Debian/Ubuntu: fonts-noto-cjk
Alpine: font-noto-cjk
Fedora: google-noto-cjk-fonts

IE for webtop the inline readme-vars.yml will look like this:

# application setup block
app_setup_block_enabled: true
app_setup_block: |
  The Webtop can be accessed at:

  * http://yourhost:3000/
  * https://yourhost:3001/

# kasm variables
kasm_blurb: true
external_http_port: "3000"
external_https_port: "3001"
noto_fonts: "font-noto-cjk"
show_nvidia: true

[LinuxServer-CI]

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https://ci-tests.linuxserver.io/lspipepr/jenkins-builder/077de28a-pkg-077de28a-dev-274fadc74589bf38faeff104093537b0c1e57088-pr-290/shellcheck-result.xml

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arm64v8-077de28a-pkg-077de28a-dev-274fadc74589bf38faeff104093537b0c1e57088-pr-290	✅

[LinuxServer-CI]

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https://ci-tests.linuxserver.io/lspipepr/jenkins-builder/077de28a-pkg-077de28a-dev-e2e748ac880fb15d6dc3d53f3185092544183d46-pr-290/shellcheck-result.xml

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arm64v8-077de28a-pkg-077de28a-dev-e2e748ac880fb15d6dc3d53f3185092544183d46-pr-290	✅

[Roxedus]

This should probably also be on the docs page, by having the same blurb in the docs template.

[Roxedus]

I think we should mention why exposing it is a bad idea, and the direct consequences.

Suggested change

	As this container has easy shell access, it makes it a prime target for automated attacks for i.e. cryptominers, but could also be used to further probe your local network,

[thelamer]

I went with From the web interface a terminal can be launched and it is configured for passwordless sudo, so anyone with access to it can install and run whatever they want along with probing your local network. let me know if this is sufficient.

[LinuxServer-CI]

I am a bot, here are the test results for this PR:
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https://ci-tests.linuxserver.io/lspipepr/jenkins-builder/077de28a-pkg-077de28a-dev-2a39d03ad61982e7ec8d12fdde5a62d27f2fb362-pr-290/shellcheck-result.xml

Tag	Passed
amd64-077de28a-pkg-077de28a-dev-2a39d03ad61982e7ec8d12fdde5a62d27f2fb362-pr-290	✅
arm64v8-077de28a-pkg-077de28a-dev-2a39d03ad61982e7ec8d12fdde5a62d27f2fb362-pr-290	✅