docs: add datefmt documentation

[skip ci]

README.md

@@ -32,6 +32,7 @@
 | [behead](/src/cmd/behead.rs#L2) | Drop headers from a CSV.  |
 | [cat](/src/cmd/cat.rs#L2)<br>🗄️ | Concatenate CSV files by row or by column. |
 | [count](/src/cmd/count.rs#L2)<br>📇🏎️ | Count the rows in a CSV file. (13.98 seconds for a 15gb, 27m row NYC 311 dataset without an index. Instantaneous with an index.) |
+| [datefmt](/src/cmd/datefmt.rs#L2)<br>🚀 | Formats recognized date fields ([19 formats recognized](https://github.com/jqnatividad/belt/tree/main/dateparser#accepted-date-formats)) to a specified date format using [strftime date format specifiers](https://docs.rs/chrono/latest/chrono/format/strftime/). |
 | [dedup](/src/cmd/dedup.rs#L2)<br>🤯🚀 | Remove duplicate rows (See also `extdedup`, `extsort`, `sort` & `sortcheck` commands). |
 | [describegpt](/src/cmd/describegpt.rs#L2)<br>🌐🤖 | Infer extended metadata about a CSV using a GPT model from [OpenAI's API](https://platform.openai.com/docs/introduction). |
 | [diff](/src/cmd/diff.rs#L2)<br>🚀 | Find the difference between two CSVs with ludicrous speed!<br/>e.g. _compare two CSVs with 1M rows x 9 columns in under 600ms!_ |
@@ -424,7 +425,7 @@ Dual-licensed under MIT or the [UNLICENSE](https://unlicense.org).
 
 ## Origins
 
-Quicksilver (qsv) is a fork of the popular [xsv](https://github.com/BurntSushi/xsv) utility, merging several pending PRs [since xsv 0.13.0's May 2018 release](https://github.com/BurntSushi/xsv/issues/267). On top of xsv's 20 commands, it adds numerous new features; 36 additional commands; 5 `apply` subcommands & 36 operations; 5 `to` subcommands; 3 `cat` subcommands; 7 `geocode` subcommands & 4 index operations; and 4 `snappy` subcommands.
+Quicksilver (qsv) is a fork of the popular [xsv](https://github.com/BurntSushi/xsv) utility, merging several pending PRs [since xsv 0.13.0's May 2018 release](https://github.com/BurntSushi/xsv/issues/267). On top of xsv's 20 commands, it adds numerous new features; 37 additional commands; 4 `apply` subcommands & 36 operations; 5 `to` subcommands; 3 `cat` subcommands; 7 `geocode` subcommands & 4 index operations; and 4 `snappy` subcommands.
 See [FAQ](https://github.com/jqnatividad/qsv/discussions/categories/faq) for more details.
 
 ## Sponsor

src/main.rs

@@ -96,7 +96,7 @@ fn main() -> QsvExitCode {
         "    behead      Drop header from CSV file
     cat         Concatenate by row or column
     count       Count records
-    datefmt     Format date and time strings
+    datefmt     Format date/datetime strings
     dedup       Remove redundant rows
     describegpt Infer extended metadata using a LLM
     diff        Find the difference between two CSVs

src/maindp.rs

@@ -55,7 +55,7 @@ macro_rules! command_list {
         "
     applydp     Apply series of transformations to a column
     count       Count records
-    datefmt     Format date and time strings
+    datefmt     Format date/datetime strings
     describegpt Infer extended metadata using a LLM
     diff        Find the difference between two CSVs
     dedup       Remove redundant rows

src/mainlite.rs

@@ -22,7 +22,7 @@ macro_rules! command_list {
     behead      Drop header from CSV file
     cat         Concatenate by row or column
     count       Count records
-    datefmt     Format date and time columns
+    datefmt     Format date/datetime columns
     dedup       Remove redundant rows
     describegpt Infer extended metadata using a LLM
     diff        Find the difference between two CSVs