(Refiles to reflect preferred name spelling in paragraph 22) By Paresh Dave and Jeffrey Dastin OAKLAND, Calif. (Reuters) -Ukrainians working at Western tech companies are banding together to help their besieged homeland, aiming to knock down disinformation websites, encourage Russians to turn against their government and speed delivery of medical supplies. They are seeking, through email campaigns and online petitions, to persuade firms such as internet security company Cloudflare Inc, Alphabet Inc’s Google and Amazon.com Inc to do more to counter Russia’s invasion of Ukraine. “Companies shoul…