readme: call out utility of joinp's asof join support for wrangli…

…ng time series data

and link to extensive examples in tests

[skip ci]

README.md

@@ -54,7 +54,7 @@
 | [index](/src/cmd/index.rs#L2) | Create an index (📇) for a CSV. This is very quick (even the 15gb, 28m row NYC 311 dataset takes all of 15 seconds to index) & provides constant time indexing/random access into the CSV. With an index, `count`, `sample` & `slice` work instantaneously; random access mode is enabled in `luau`; and multithreading (🏎️) is enabled for the `frequency`, `split`, `stats`, `schema` & `tojsonl` commands. |
 | [input](/src/cmd/input.rs#L2) | Read CSV data with special commenting, quoting, trimming, line-skipping & non-UTF8 encoding handling rules. Typically used to "normalize" a CSV for further processing with other qsv commands. |
 | [join](/src/cmd/join.rs#L2) | Inner, outer, right, cross, anti & semi joins. Automatically creates a simple, in-memory hash index to make it fast.  |
-| [joinp](/src/cmd/joinp.rs#L2)<br>✨🚀🐻‍❄️ | Inner, outer, cross, anti, semi & asof joins using the [Pola.rs](https://www.pola.rs) engine. Unlike the `join` command, `joinp` can process files larger than RAM, is multi-threaded, has join key validation, pre-join filtering, supports [asof joins](https://pola-rs.github.io/polars/py-polars/html/reference/dataframe/api/polars.DataFrame.join_asof.html) & its output doesn't have duplicate columns. However, `joinp` doesn't have an --ignore-case option & it doesn't support right outer joins. |
+| [joinp](/src/cmd/joinp.rs#L2)<br>✨🚀🐻‍❄️ | Inner, outer, cross, anti, semi & asof joins using the [Pola.rs](https://www.pola.rs) engine. Unlike the `join` command, `joinp` can process files larger than RAM, is multi-threaded, has join key validation, pre-join filtering, supports [asof joins](https://pola-rs.github.io/polars/py-polars/html/reference/dataframe/api/polars.DataFrame.join_asof.html) (which is [particularly useful for time series data](https://github.com/jqnatividad/qsv/blob/30cc920d0812a854fcbfedc5db81788a0600c92b/tests/test_joinp.rs#L509-L983)) & its output doesn't have duplicate columns. However, `joinp` doesn't have an --ignore-case option & it doesn't support right outer joins. |
 | [jsonl](/src/cmd/jsonl.rs#L2)<br>🔣 | Convert newline-delimited JSON ([JSONL](https://jsonlines.org/)/[NDJSON](http://ndjson.org/)) to CSV. See `tojsonl` command to convert CSV to JSONL.
 | <a name="luau_deeplink"></a><br>[luau](/src/cmd/luau.rs#L2) 👑<br>✨📇🌐🔣 ![CKAN](docs/images/ckan.png) | Create multiple new computed columns, filter rows, compute aggregations and build complex data pipelines by executing a [Luau](https://luau-lang.org) [0.606](https://github.com/Roblox/luau/releases/tag/0.606) expression/script for every row of a CSV file ([sequential mode](https://github.com/jqnatividad/qsv/blob/bb72c4ef369d192d85d8b7cc6e972c1b7df77635/tests/test_luau.rs#L254-L298)), or using [random access](https://www.webopedia.com/definitions/random-access/) with an index ([random access mode](https://github.com/jqnatividad/qsv/blob/bb72c4ef369d192d85d8b7cc6e972c1b7df77635/tests/test_luau.rs#L367-L415)).<br>Can process a single Luau expression or [full-fledged data-wrangling scripts using lookup tables](https://github.com/dathere/qsv-lookup-tables#example) with discrete BEGIN, MAIN and END sections.<br> It is not just another qsv command, it is qsv's [Domain-specific Language](https://en.wikipedia.org/wiki/Domain-specific_language) (DSL) with [numerous qsv-specific helper functions](https://github.com/jqnatividad/qsv/blob/113eee17b97882dc368b2e65fec52b86df09f78b/src/cmd/luau.rs#L1356-L2290) to build production data pipelines. |
 | [partition](/src/cmd/partition.rs#L2) | Partition a CSV based on a column value. |