Update service provider page: Put focus on the "contribute your service" part

As a user and potential service provider (or knowing someone who could become a service provider), I'd be interested to quickly see information on how to do so and even be encouraged to do so.

Propose to:

Not this MR: Put a link in the portal 👉 hifis/cloud/access-layer/portal#143 (closed)

Reshuffle the cloud provider page a bit; away from the descriptive stuff and more towards the "We want your contribution" message:

• Move the "Becoming a service provider" section up and formulate a bit more openly ("You think about contributing a new cloud service? Here's how:")

• Add Incentives and Doubts without putting too much emphasis on the latter

  • Focus on what we are interested in and take away the obstacles that people often stumble over: Scientific/Community services, small/focused/dedicated services appreciated, no need to provide productive services from start on, no need to provide endless resources to all Helmholtz (which people often fear to have to).

• Technical documentation and details can be moved downwards then

• 👉 Review here

• 👉 Review Sub-Page

• 👉 Edit here

• 👉 Edit Word-Doc of Benefits and doubts

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Closes #422 (closed)