Add support for upsert

[josiahsrc]

Is your feature request related to a problem? Please describe.
A lot of the time I need to either insert data or update existing data (depending on if it's created or not).

Describe the solution you'd like
Add upsert functionality.

Describe alternatives you've considered
A query followed by an insert or update.

data = supabase.table('table').select(*).eq('id', 'something').execute()
if len(data.get('id', [])) > 0:
  // update the data
else:
  // insert the data

Additional context
Taken from the supabase docs, I couldn't find this functionality in this library. Does something to this effect exist yet?

const { data, error } = await supabase
  .from('messages')
  .upsert({ id: 3, message: 'foo', username: 'supabot' })