add sparsity to stats description

[skip ci]

README.md

@@ -72,7 +72,7 @@ See [FAQ](https://github.com/jqnatividad/qsv/discussions/categories/faq) for mor
 | [sort](/src/cmd/sort.rs#L2)<br>🚀🗜️ | Sorts CSV data in alphabetical (with case-insensitive option), numerical, reverse, unique or random (with optional seed) order (See also `extsort` & `sortcheck` commands).  |
 | [sortcheck](/src/cmd/sortcheck.rs#L2)<br>📇 | Check if a CSV is sorted. With the --json options, also retrieve record count, sort breaks & duplicate count. |
 | [split](/src/cmd/split.rs#L2)<br>📇🏎️ | Split one CSV file into many CSV files of N chunks. Uses multithreading to go faster if an index is present. |
-| [stats](/src/cmd/stats.rs#L2)<br>📇🗜️🏎️ | Compute [summary statistics](https://en.wikipedia.org/wiki/Summary_statistics) (sum, min/max/range, min/max length, mean, stddev, variance, nullcount, quartiles, IQR, lower/upper fences, skewness, median, mode/s, antimode/s & cardinality) & infer data type (Null, String, Float, Integer, Date, DateTime) for each column in a CSV. Uses multithreading to go faster if an index is present. |
+| [stats](/src/cmd/stats.rs#L2)<br>📇🗜️🏎️ | Compute [summary statistics](https://en.wikipedia.org/wiki/Summary_statistics) (sum, min/max/range, min/max length, mean, stddev, variance, nullcount, sparsity, quartiles, IQR, lower/upper fences, skewness, median, mode/s, antimode/s & cardinality) & infer data type (Null, String, Float, Integer, Date, DateTime) for each column in a CSV. Uses multithreading to go faster if an index is present. |
 | [table](/src/cmd/table.rs#L2)<br>🗜️ | Show aligned output of a CSV using [elastic tabstops](https://github.com/BurntSushi/tabwriter).  |
 | [to](/src/cmd/to.rs#L2)<br>❇️🚀 | Convert CSV files to [PostgreSQL](https://www.postgresql.org), [SQLite](https://www.sqlite.org/index.html), XLSX, [Parquet](https://parquet.apache.org) and [Data Package](https://datahub.io/docs/data-packages/tabular). |
 | [tojsonl](/src/cmd/tojsonl.rs#L2)<br>📇🏎️ | Smartly converts CSV to a newline-delimited JSON ([JSONL](https://jsonlines.org/)/[NDJSON](http://ndjson.org/)). By scanning the CSV first, it "smartly" infers the appropriate JSON data type for each column. See `jsonl` command to convert JSONL to CSV. Uses multithreading to go faster if an index is present. |