Add --separator command to from_csv

The command takes a string, checks it is a single character and then
passes it to csv::ReaderBuilder via .delimiter() method as a u8.

docs/commands/from-csv.md

@@ -3,7 +3,9 @@
 Converts csv data into table. Use this when nushell cannot dertermine the input file extension.
 
 ## Example
+
 Let's say we have the following file :
+
 ```shell
 > cat pets.txt
 animal, name, age
@@ -36,6 +38,7 @@ To get a table from `pets.txt` we need to use the `from-csv` command :
 ```
 
 To ignore the csv headers use `--headerless` :
+
 ```shell
 ━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━━━━
  # │ Column1   │ Column2 │ Column3
@@ -45,3 +48,65 @@ To ignore the csv headers use `--headerless` :
 ━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━━━━
 ```
 
+To split on a character other than ',' use `--separator` :
+
+```shell
+> open pets.txt
+animal; name; age
+cat; Tom; 7
+dog; Alfred; 10
+chameleon; Linda; 1
+```
+
+```shell
+> open pets.txt | from-csv --separator ';'
+━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━
+ # │ animal    │  name   │  age
+───┼───────────┼─────────┼──────
+ 0 │ cat       │  Tom    │  7
+ 1 │ dog       │  Alfred │  10
+ 2 │ chameleon │  Linda  │  1
+━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━
+```
+
+To use this command to open a csv with separators other than a comma, use the `--raw` switch of `open` to open the csv, othewise the csv will enter `from-csv` as a table split on commas rather than raw text.
+
+```shell
+> mv pets.txt pets.csv
+> open pets.csv | from-csv --separator ';'
+error: Expected a string from pipeline
+- shell:1:16
+1 | open pets.csv | from-csv --separator ';'
+  |                 ^^^^^^^^ requires string input
+- shell:1:0
+1 | open pets.csv | from-csv --separator ';'
+  |  value originates from here
+
+> open pets.csv --raw | from-csv --separator ';'
+━━━┯━━━━━━━━━━━┯━━━━━━━━━┯━━━━━━
+ # │ animal    │  name   │  age
+───┼───────────┼─────────┼──────
+ 0 │ cat       │  Tom    │  7
+ 1 │ dog       │  Alfred │  10
+ 2 │ chameleon │  Linda  │  1
+━━━┷━━━━━━━━━━━┷━━━━━━━━━┷━━━━━━
+```
+
+Note that separators are currently provided as strings and need to be wrapped in quotes.
+
+```shell
+> open pets.csv --raw | from-csv --separator ;
+- shell:1:43
+1 | open pets.csv --raw | from-csv --separator ;
+  |                                            ^
+```
+
+It is also considered an error to use a separator greater than one char :
+
+```shell
+> open pets.txt | from-csv --separator '123'
+error: Expected a single separator char from --separator
+- shell:1:37
+1 | open pets.txt | from-csv --separator '123'
+  |                                      ^^^^^ requires a single character string input
+```