Add new training materials

[LionelJouin]

Is your feature request related to a problem? Please describe.
The idea is to improve the learning materials for Meridio.
We will now have a dedicated menu on the Meridio website: https://website.meridio.pages.dev/training and 3 types of materials:

• Youtube
• Killercoda
• asciinema

Describe the solution you'd like
Scenarios:

• Playground
• Course
  • Installation
  • Traffic Path
  • Health check (how to know if everything works fine)
  • Target Registration
  • Control plane
  • Attractor types
    • NSM VLAN
    • NSM base interface
    • Multus*
  • Gateway routing protocols
    • BGP (how it works, BGP authentication...)
    • BFD
    • Static Routing*
  • Conduit types
    • Stateless load-balancer
• Use-Cases
  • Network Separation
  • External Traffic Attraction
  • Network Services (Stateless-lb, NAT, No NAT, Flow...)
  • Runtime Configuration
• Troubleshooting CTF
  • Misconfiguration of the Gateways
    • Wrong ports
    • Wrong IPs
    • Wrong protocol
    • Wrong ASN
  • Misconfiguration of the attractors
    • Wrong subnet
    • Wrong VLAN ID
    • Wrong base interface*
    • MTU mismatch*
    • Usage of NSM VLAN on a base interface which is already a VLAN
    • Allocated IP is the same as the gateway one
  • Misconfiguration of the streams/flows
    • Traffic goes in the wrong stream due to flow priority
    • Port not opened
    • Port opened but restricted due to byte-match
  • Misconfiguration of the VIPs
    • VIP configured in the flow but not in the attractor
  • Misconfiguration of the TAPA
    • TAPA running in another namespace but MERIDIO_NAMESPACE not set
    • MERIDIO_NSP_SERVICE_NAME / MERIDIO_NSP_SERVICE_PORT changed
    • Wrong stream opened
    • Wrong conduit opened
    • Wrong trench opened
  • NSM issue
    • target <-> proxy xconnect broken
    • LB <-> proxy VxLAN broken
  • Installation
    • Spire not installed
    • NSM not installed
  • Kubernetes primary network conflict
    • Pod subnet conflicting with internal Meridio subnet
    • Service subnet conflicting with internal Meridio subnet
    • DNS server conflicting with internal Meridio subnet
    • VIP in Pod Subnet range
    • VIP in internal Meridio subnet

(*) Requires improvements of the current Kind setup

Describe alternatives you've considered
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Additional context
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