Vi-style editor and other editor improvements (#40)

* WIP VI wrapper for editor

* WIP: block cursor

* Create Edit trait, run CI on all feature options

* Add prints describing build steps to ci.sh

* Custom rendering for Vi editor

* Clippy fixes

* More clippy fixes

* Show clippy results in CI

* Fix for Redox

* Fix clippy lint

* Add vi feature to enable vi-style editor

* Add escape to libcosmic text box

ci.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+function build {
+    cargo build --release "$@"
+    cargo clippy --no-deps "$@"
+}
+
+set -ex
+
+echo Build with default features
+build
+
+echo Build with no default features
+build --no-default-features
+
+echo Build with only std feature
+build --no-default-features --features std
+
+echo Build with only swash feature
+build --no-default-features --features swash
+
+echo Build with only syntect feature
+build --no-default-features --features syntect
+
+echo Build with only vi feature
+build --no-default-features --features vi
+
+echo Build with all features
+build --all-features
+
+echo Run tests
+cargo test