Input:
^{_{tellraw @a [{"text":"Timber Datapack V14 installed!","color":"dark_green"},{"text":"\n[click here to check for new updates]","color":"gold","clickEvent":{"action":"open_url","value":"https://www.planetminecraft.com/data-pack/timber-datapack/"}}]}}
Output (1.15 and above):

Output (1.14):

(Nice Datapack download it)