feat: Document /acts/ACTOR-ID/validate-input endpoint#2384

gemini-25-pro-collab wants to merge 1 commit intoapify:masterapify/apify-docs:masterfrom

gemini-25-pro-collab:document-validate-input-endpointgemini-25-pro-collab/apify-docs:document-validate-input-endpointCopy head branch name to clipboard