reviewflags table doesn't have a primary key

[dfabulich]

https://github.com/iftechfoundation/ifdb/blob/main/sql/patch-schema.sql#L146-L154

CREATE TABLE `reviewflags` (
  `reviewid` bigint(20) NOT NULL,
  `flagger` varchar(32) COLLATE latin1_german2_ci NOT NULL,
  `flagtype` char(1) COLLATE latin1_german2_ci NOT NULL,
  `notes` mediumtext COLLATE latin1_german2_ci,
  `created` datetime NOT NULL,
  KEY `reviewid` (`reviewid`),
  KEY `flagger` (`flagger`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_german2_ci;

This table doesn't have a primary key. reviewid is a foreign key to the reviews table.

As a result, if you try to poke around this table in phpMyAdmin, it says, "Current selection does not contain a unique column. Grid edit, checkbox, Edit, Copy and Delete features are not available."

We should add an autoincrementing primary key id to make that message go away and make it easier to work with this table.