Add ansi escape codes

text/0000-add-ansi-escape-codes.md

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+- Feature Name: add_ansi_escape_codes
+- Start Date: 2022-02-14
+- RFC PR: (leave this empty)
+- Pony Issue: (leave this empty)
+
+# Summary
+
+This RFC proposes the addition of more escape code functions to the ANSI primitive of the term package and the consolidation of the thirty-two existing color functions into four functions.
+
+# Motivation
+
+The purpose of these additional methods is to cover more of the standard ANSI escape codes within the stdlib.
+
+# Detailed design
+
+- Add escape codes for 3-bit, 4-bit, 8-bit, and 24-bit colors for the foreground and background.  
+The naming scheme of the color functions would be `{fg,bg}_{3,4,8,24}bit`.  
+The 3-bit, 4-bit, and 8-bit versions would take a U8 specifying the color.  
+The 24-bit versions would take three U8s specifying the r, g, and b values.  
+- Remove the thirty-two named color functions in favor of the 3-bit and 4-bit functions.
+- Add escape codes for enter and leave alternate screen buffer.
+- Add escape code for the bell alert.
+- Change `clear` and `erase` functions to take a U8 specifying what part of the screen/line to clear.  
+The default for the escape codes if a value isn't given is zero.  
+The action these functions currently take is three for `clear` and one for `erase`.  
+I would like to have the default value in these functions be zero.
+- Add escape codes for scroll up/down.
+- Add escape codes for next/previous line.
+- Add escape code for cursor horizontal position (moves the cursor to column n in the current line).
+- Add escape codes for hide/show cursor.
+- Add escape codes for save/restore cursor position.
+- Add escape code for get cursor position (it is sent to stdin).
+- Add escape codes for various text styles: italic, strike, conceal, faint.
+
+If a value passed to any of the functions is invalid, such as 200 being passed to `fg_3bit`, an empty string would be returned.
+
+# How We Teach This
+
+The added functions would be documented as the existing functions on the `ANSI` primitive are and an example of usage would be added to `ANSI`.
+
+# How We Test This
+
+I could not find existing testing for the `ANSI` primitive.  
+If there are existing tests for these functions, additional tests in the same format would be added to ensure that the new functions return the correct escape codes.  
+Most of these functions are just directly returning a string of the escape code without any parameters so they're pretty straightforward.
+
+# Drawbacks
+
+The removal of the existing color functions and the change to the `clear` and `erase` functions (if the default of zero is used) are breaking changes.
+
+# Alternatives
+
+## Alternative to the rfc as a whole
+These escape codes can simply be printed independently of whatever is supported by functions on `ANSI`.  
+Having them available on `ANSI` simply makes it so that users do not need to look the codes up themselves.
+
+## Alternative to the breaking changes
+The existing color functions could remain and the 3-bit and 4-bit color functions could exist alongside them or not be implemented.  
+The `clear` and `erase` functions could have default values that match their existing behavior.
+
+# Unresolved questions
+
+Should the breaking changes be made to simplify the interface?