Added docs for most of the to-sth commands

Partial fix of issue #711
Docs for the following commands were added -
to-csv
to-json
to-toml
to-tsv
to-url
to-yaml

Docs for to-db , to-bson , to-sqlite have not been added as I don't recognize and understand those formats.

docs/commands/to-csv.md

@@ -0,0 +1,21 @@
+# to-csv
+
+Converts table data into csv text.
+
+## 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
+```