Add :os tty module

- Moves clipetty to its own, opt-in module (#2671, #3195, #3498)
- Fix cursor shape changing between evil states (#1994)
- Moves `xterm-mouse-mode` and `visible-cursor` config out of core.

modules/os/tty/README.org

@@ -0,0 +1,59 @@
+#+TITLE:   os/tty
+#+DATE:    August 7, 2020
+#+SINCE:   v3.0.0
+#+STARTUP: inlineimages nofold
+
+* Table of Contents :TOC_3:noexport:
+- [[#description][Description]]
+  - [[#maintainers][Maintainers]]
+  - [[#module-flags][Module Flags]]
+  - [[#plugins][Plugins]]
+- [[#prerequisites][Prerequisites]]
+- [[#configuration][Configuration]]
+- [[#troubleshooting][Troubleshooting]]
+
+* Description
+This module configures Emacs for terminal usage.
+
++ System clipboard integration (through an external clipboard program or OSC-52
+  escape codes in supported terminals).
++ Fixes cursor-shape changing across evil states in terminal that support it.
++ Mouse support in the terminal.
+
+** Maintainers
+This module has no dedicated maintainers.
+
+** Module Flags
++ =+osx= Instead of piping your kill ring through external programs, like xclip
+  or pbcopy, have Emacs emit OSC-52 escape codes instead, allowing Emacs to
+  communicate to your clipboard through your terminal. This allows for clipboard
+  communication over SSH connections or tmux. However, this requires [[https://github.com/spudlyo/clipetty#terminals-that-support-osc-clipboard-operations][a supported
+  terminal]].
+
+** Plugins
++ clipetty
++ evil-terminal-cursor-changer
++ xclip
+
+* Prerequisites
+This module has no hard prerequisites, but in order for its features to work you
+need
+
++ For system clipboard integration:
+  + A supported clipboard program, such as:
+    + Linux: =xclip=, =xsel=, or =wl-clibpoard= (Wayland)
+    + macOS: =pbcopy= and =pbpaste= (included with macOS)
+    + Windows: =getclip= and =putclip= (cygwin)
+  + A terminal that supports OSC 52 escape codes, such as:
+    xterm (unix), iTerm2 (macOS), alacritty (cross platform), kitty (macOS, linux), mintty (Windows), hterm (javascript), st (unix), mlterm (cross platform)
++ For cursor shape changing:
+  + A terminal that supports VT's DECSCUSR sequence, such as:
+    Gnome Terminal, xterm, iTerm (macOS), Konsole, or mintty (Windows).
+    Terminal.app (macOS) is supported to, but requires [[http://www.culater.net/software/SIMBL/SIMBL.php][SIMBL]] and [[https://github.com/saitoha/mouseterm-plus/releases][MouseTerm]] Plus
+    to work.
+
+* Configuration
+# How to configure this module, including common problems and how to address them.
+
+* Troubleshooting
+# Common issues and their solution, or places to look for help.