Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/seq_date.md

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+---
+title: seq date
+layout: command
+version: 0.59.0
+---
+
+print sequences of dates
+
+## Signature
+
+```> seq date --separator --output-format --input-format --begin-date --end-date --increment --days --reverse```
+
+## Parameters
+
+ -  `--separator {string}`: separator character (defaults to \n)
+ -  `--output-format {string}`: prints dates in this format (defaults to %Y-%m-%d)
+ -  `--input-format {string}`: give argument dates in this format (defaults to %Y-%m-%d)
+ -  `--begin-date {string}`: beginning date range
+ -  `--end-date {string}`: ending date
+ -  `--increment {int}`: increment dates by this number
+ -  `--days {int}`: number of days to print
+ -  `--reverse`: print dates in reverse
+
+## Examples
+
+print the next 10 days in YYYY-MM-DD format with newline separator
+```shell
+> seq date --days 10
+```
+
+print the previous 10 days in YYYY-MM-DD format with newline separator
+```shell
+> seq date --days 10 -r
+```
+
+print the previous 10 days starting today in MM/DD/YYYY format with newline separator
+```shell
+> seq date --days 10 -o '%m/%d/%Y' -r
+```
+
+print the first 10 days in January, 2020
+```shell
+> seq date -b '2020-01-01' -e '2020-01-10'
+```
+
+print every fifth day between January 1st 2020 and January 31st 2020
+```shell
+> seq date -b '2020-01-01' -e '2020-01-31' -n 5
+```
+
+starting on May 5th, 2020, print the next 10 days in your locale's date format, colon separated
+```shell
+> seq date -o %x -s ':' -d 10 -b '2020-05-01'
+```
+