feat: update changelog (#131)

closes #130 

- CHANGELOG.md file for people who can view changelog from github
---
`iris changelog` command:
`iris changelog [version]` (e.g. iris changelog v0.5.1)
`iris changelog -n 3` (see changelog of 3 latest releaseas)

=> `iris changelog` looks just like CHANGELOG.md, grouped headers and
all. It only stops looking that way if we personally overwrite that
release's description with something else
=> With 1-hour local cache (invalidated on updater-channel change),
`--refresh` flag to bypass, graceful fallback to stale cache on GitHub
rate-limiting

---
- New auto update config
```toml
# 0 = off (default, notify only), 1 = auto-install, 2 = always confirm first
auto-update = 1
```

- New just debug-changelog and just debug-autoupdate recipes (fully
offline, mocked HTTP servers, no real network/config touched)

root/wrapper.go

@@ -555,7 +555,17 @@ func runWrapper() {
 					select {
 					case result, ok := <-pendingUpdate:
 						if ok && result.hasUpdate {
-							printUpdateNotice(result.latestVersion)
+							switch result.kind {
+							case updateResultAutoInstalled:
+								printAutoUpdateInstalledNotice(result.latestVersion)
+							case updateResultConfirm:
+								printAutoUpdateConfirmPrompt(result.latestVersion, result.notes)
+								armAutoUpdateConfirm(result.latestVersion)
+							case updateResultGiveUp:
+								printAutoUpdateGiveUpNotice(result.latestVersion)
+							default:
+								printUpdateNotice(result.latestVersion, result.notes)
+							}
 							updatePrinted = true
 						}
 					default:
@@ -778,6 +788,12 @@ func runWrapper() {
 				b := inputSlice[i]
 				intercepted = false
 
+				// while an auto-update confirm prompt is pending, every
+				// byte goes to it instead of normal key handling
+				if handleAutoUpdateConfirmKey(b) {
+					continue
+				}
+
 				if matched, consumed := config.MatchKey(inputSlice[i:], config.Get().Keybindings.ToggleMenu); matched {
 					intercepted = true
 					suggestionsEnabled = !suggestionsEnabled