docs: add sum & avg length

[skip ci]

README.md

@@ -80,7 +80,7 @@
 | [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. It can split by number of rows, number of chunks or file size. Uses multithreading to go faster if an index is present when splitting by rows or chunks. |
 | [sqlp](/src/cmd/sqlp.rs#L2)<br>✨🚀🐻‍❄️🗄️ | Run [Polars](https://pola.rs) SQL queries against several CSVs - converting queries to blazing-fast [LazyFrame](https://docs.pola.rs/user-guide/lazy/using/) expressions, processing larger than memory CSV files. Query results can be saved in CSV, JSON, JSONL, Parquet, Apache Arrow IPC and Apache Avro formats. |
-| [stats](/src/cmd/stats.rs#L2)<br>📇🤯🏎️👆🪄 | Compute [summary statistics](https://en.wikipedia.org/wiki/Summary_statistics) (sum, min/max/range, sort order, min/max length, mean, standard error of the mean (SEM), stddev, variance, Coefficient of Variation (CV), nullcount, max precision, sparsity, quartiles, Interquartile Range (IQR), lower/upper fences, skewness, median, mode/s, antimode/s & cardinality) & make GUARANTEED data type inferences (Null, String, Float, Integer, Date, DateTime, Boolean) for each column in a CSV ([more info](https://github.com/jqnatividad/qsv/wiki/Supplemental#stats-command-output-explanation)).<br>Uses multithreading to go faster if an index is present (with an index, can compile "streaming" stats on NYC's 311 data (15gb, 28m rows) in less than 7.3 seconds!). |
+| [stats](/src/cmd/stats.rs#L2)<br>📇🤯🏎️👆🪄 | Compute [summary statistics](https://en.wikipedia.org/wiki/Summary_statistics) (sum, min/max/range, sort order, min/max/sum/avg length, mean, standard error of the mean (SEM), stddev, variance, Coefficient of Variation (CV), nullcount, max precision, sparsity, quartiles, Interquartile Range (IQR), lower/upper fences, skewness, median, mode/s, antimode/s & cardinality) & make GUARANTEED data type inferences (Null, String, Float, Integer, Date, DateTime, Boolean) for each column in a CSV ([more info](https://github.com/jqnatividad/qsv/wiki/Supplemental#stats-command-output-explanation)).<br>Uses multithreading to go faster if an index is present (with an index, can compile "streaming" stats on NYC's 311 data (15gb, 28m rows) in less than 7.3 seconds!). |
 | [table](/src/cmd/table.rs#L2)<br>🤯 | Show aligned output of a CSV using [elastic tabstops](https://github.com/BurntSushi/tabwriter).  To interactively view CSV files, qsv pairs well with [csvlens](https://github.com/YS-L/csvlens#csvlens). |
 | [to](/src/cmd/to.rs#L2)<br>✨🚀🗄️ | Convert CSV files to [PostgreSQL](https://www.postgresql.org), [SQLite](https://www.sqlite.org/index.html), XLSX and [Data Package](https://datahub.io/docs/data-packages/tabular). |
 | [tojsonl](/src/cmd/tojsonl.rs#L3)<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. |