datadog: enrich offer economics, benefits and eligibility from live site

[Larslllllll]

What changed

Updated entities/da/datadog.yaml with richer offer details sourced from datadoghq.com/partner/datadog-for-startups:

• consideration.kind: unknown → free (corrected from live site facts)
• benefit[ben_primary]: expanded to describe full platform access, GA products, no tier restrictions or hidden limits
• benefit[ben_onboarding]: added TEM (technical engagement manager) onboarding support
• eligibility.statement: clarified referral partner categories (VCs, hyperscalers, vendor partner startup programs)
• summary: tightened to front-load $100k credit value and "no watered-down tiers"

Sources

• https://www.datadoghq.com/partner/datadog-for-startups/ (FAQ and program page)

Certification

• I changed only allowed repository content and did not mix Entity YAML with other paths.
• Public sources substantiate every submitted factual value; any Sourcey-written prose is a neutral summary, not a fabricated vendor quote.
• I did not author verification, provenance, freshness, or signature claims.
• My commits include a Signed-off-by line.

[Larslllllll]

I've created PR sourcey#1439 that enriches the Datadog offer as requested.

Changes:

• Changed consideration.kind from unknown to free
• Expanded ben_primary to describe full platform access with GA products
• Added ben_onboarding for TEM (Technical Engagement Manager) support
• Clarified eligibility statement with referral partner categories (VCs, hyperscalers, vendor partner startup programs)