Add blob: to allowed img-src rules in CSP (#4860)
Add blob: to allowed img-src rules in CSP (#4860)

This is needed for Plotly download PNG feature to work.
alexanderlz/redash,getredash/redash,denisov-vlad/redash,getredash/redash,denisov-vlad/redash,alexanderlz/redash,denisov-vlad/redash,getredash/redash,alexanderlz/redash,denisov-vlad/redash,getredash/redash,denisov-vlad/redash,getredash/redash,alexanderlz/redash