How many mills of 'Grondzeiler' type are built in each year? Give me the trend.
CREATE TABLE bridge (
    architect_id int,
    id int,
    name text,
    location text,
    length_meters real,
    length_feet real
)

CREATE TABLE architect (
    id text,
    name text,
    nationality text,
    gender text
)

CREATE TABLE mill (
    architect_id int,
    id int,
    location text,
    name text,
    type text,
    built_year int,
    notes text
)
SELECT built_year, COUNT(built_year) FROM mill WHERE type = 'Grondzeiler'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many mills of 'Grondzeiler' type are built in each year? Give me the trend. ### Input: CREATE TABLE bridge (
    architect_id int,
    id int,
    name text,
    location text,
    length_meters real,
    length_feet real
)

CREATE TABLE architect (
    id text,
    name text,
    nationality text,
    gender text
)

CREATE TABLE mill (
    architect_id int,
    id int,
    location text,
    name text,
    type text,
    built_year int,
    notes text
) ### Response: SELECT built_year, COUNT(built_year) FROM mill WHERE type = 'Grondzeiler'