Table: `Followers`

    +-------------+------+
    | Column Name | Type |
    +-------------+------+
    | user_id     | int  |
    | follower_id | int  |
    +-------------+------+
    (user_id, follower_id) is the primary key for this table.
    This table contains the IDs of a user and a follower in a social media app where the follower follows the user.

Write an SQL query that will, for each user, return the number of followers.

Return the result table ordered by `user_id`.

The query result format is in the following example.

Example 1:

    Input:
    Followers table:
    +---------+-------------+
    | user_id | follower_id |
    +---------+-------------+
    | 0       | 1           |
    | 1       | 0           |
    | 2       | 0           |
    | 2       | 1           |
    +---------+-------------+
    Output:
    +---------+----------------+
    | user_id | followers_count|
    +---------+----------------+
    | 0       | 1              |
    | 1       | 1              |
    | 2       | 2              |
    +---------+----------------+
    Explanation:
    The followers of 0 are {1}
    The followers of 1 are {0}
    The followers of 2 are {0,1}