Add documentation for the Search V2 API

[teolemon]

What

• Add documentation for the Search V2 API

examples

• https://world.openfoodfacts.org/api/v2/search?categories_tags_en=cakes&fields=code,product_name&sort_by=ecoscore_score
• https://world.openfoodfacts.org/api/v2/search?ingredients_analysis_tags=en:vegan&fields=code,product_name
• https://fr.openfoodfacts.org/api/v2/search?fields=code,product_name,knowledge_panels&page_size=1000
• https://world.openfoodfacts.org/api/v2/search?categories_tags=en:hazelnut-spreads&fields=id,categories_tags
• https://world.openfoodfacts.net/api/v2/search?page_size=10&fields=id,image_front_url
• https://world.openfoodfacts.org/api/v2/search?sort_by=last_modified_t
• https://nl.openfoodfacts.org/api/v2/search?ingredients_analysis_tags=en:vegan&stores_tags=Delhaize&fields=code
• https://openfoodfacts.org/api/v2/search?code=3352915400008&page_size=1&no_cache=1&fields=code,product_name,ecoscore_extended_data
• https://openfoodfacts.net/api/v2/search?states_tags=en:ingredients-completed,en:nutrition-facts-completed&misc_tags=-en:ecoscore-extended-data-version-2&fields=code&page_size=1&sort_by=nothing&no_cache=1
• https://world.openfoodfacts.org/api/v2/search?code=8024884500403,3263855093192&fields=code,product_name (replaces https://world.openfoodfacts.org/products/8024884500403,3263855093192,3045320001570,3021762383344,4008400402222,3330720237255,3608580823513,3700278403936,3302747010029,3608580823490,3250391660995,3760020506605,8722700202387,3330720237330,3535800940005,20000691,3270190127512)
• https://us.openfoodfacts.org/api/v2/search?categories_tags_en=snacks&allergens_tags:=-en:gluten&page_size=5
• https://uk.openfoodfacts.org/api/v2/search?salt_100g=%3E10&salt_100g=%3C15&fields=code,product_name,salt_100g