fix(uploads): Display icon regardless of ext capitalization
fix(uploads): Display icon regardless of ext capitalization

Note: In the future we really need to consolidate file-upload.cjsx and attachment-component.cjsx. #1700

simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,simonft/nylas-mail,nylas/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nylas/nylas-mail,nylas/nylas-mail,simonft/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail,nirmit/nylas-mail,nylas-mail-lives/nylas-mail,nirmit/nylas-mail