docs/commands: add to.md, update subcommands (#1715)

This adds a top-level document for the new `to` command, with a list (of links) of all the subcommands.

All the to-* subcommands keep their filename, but the content is updated to use the new subcommand syntax.

Since not all subcommands have documentation, some items in the list are just text without a link. Also filled the list for the undocumented from* commands in the same style.

Fixes #1709

docs/commands/to.md

@@ -0,0 +1,47 @@
+# to
+
+Converts table data into a string or binary. The target format is specified as a subcommand, like `to csv` or `to json`.
+
+## Available Subcommands
+
+* to bson
+* [to csv](to-csv.md)
+* to html
+* [to json](to-json.md)
+* to md
+* to sqlite
+* [to toml](to-toml.md)
+* [to tsv](to-tsv.md)
+* [to url](to-url.md)
+* [to yaml](to-yaml.md)
+
+*Subcommands without links are currently missing their documentation.*
+
+## Example
+
+```shell
+> shells
+━━━┯━━━┯━━━━━━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━
+ # │   │ name       │ path
+───┼───┼────────────┼────────────────────────
+ 0 │ X │ filesystem │ /home/shaurya
+ 1 │   │ filesystem │ /home/shaurya/Pictures
+ 2 │   │ filesystem │ /home/shaurya/Desktop
+━━━┷━━━┷━━━━━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━
+> shells | to csv
+ ,name,path
+X,filesystem,/home/shaurya
+ ,filesystem,/home/shaurya/Pictures
+ ,filesystem,/home/shaurya/Desktop
+```
+
+```shell
+> open sample.url
+━━━━━━━━━━┯━━━━━━━━┯━━━━━━┯━━━━━━━━
+ bread    │ cheese │ meat │ fat
+──────────┼────────┼──────┼────────
+ baguette │ comté  │ ham  │ butter
+━━━━━━━━━━┷━━━━━━━━┷━━━━━━┷━━━━━━━━
+> open sample.url  | to url
+bread=baguette&cheese=comt%C3%A9&meat=ham&fat=butter
+```