Let the sidebar be resized by dragging its edge

The sidebar's right edge is now a splitter, like the one between the
message list and the reading pane: drag it between 240 and 480px, move it
with the arrow keys, double-click to put it back. The width is a device
setting, and stays null until someone drags, so a width set in the
reader's own CSS through --sidebar-w is kept until they choose otherwise.
Hidden on a phone, where the sidebar is a drawer, and while collapsed.

Arrow keys on either splitter moved the pane and never saved it: the
keyboard path called onResize without onEnd. It ends each key press now,
and both views keep the in-progress size in a ref as well as state, so
the end reads the value set in the same tick.

The message-list splitter's accessible name was an untranslated literal.
It goes through translate() now, and it and the sidebar's new name are in
all nine catalogues.

Closes #345

web/src/locales/de.ts

@@ -1212,6 +1212,8 @@ export const catalog: Catalog = {
     "Maximize": "Maximieren",
     "Full screen": "Vollbild",
     "Resize panes": "Bereichsgröße ändern",
+    "Resize message list": "Größe der Nachrichtenliste ändern",
+    "Resize sidebar": "Größe der Seitenleiste ändern",
     "QR code": "QR-Code",
     "Draft discarded": "Entwurf verworfen",
     "Draft saved": "Entwurf gespeichert",

web/src/locales/es.ts

@@ -1185,6 +1185,8 @@ export const catalog: Catalog = {
     "Maximize": "Maximizar",
     "Full screen": "Pantalla completa",
     "Resize panes": "Cambiar el tamaño de los paneles",
+    "Resize message list": "Cambiar el tamaño de la lista de mensajes",
+    "Resize sidebar": "Cambiar el tamaño de la barra lateral",
     "QR code": "Código QR",
     "Draft discarded": "Borrador descartado",
     "Draft saved": "Borrador guardado",

web/src/locales/fr.ts

@@ -1190,6 +1190,8 @@ export const catalog: Catalog = {
     "Maximize": "Agrandir",
     "Full screen": "Plein écran",
     "Resize panes": "Redimensionner les volets",
+    "Resize message list": "Redimensionner la liste des messages",
+    "Resize sidebar": "Redimensionner la barre latérale",
     "QR code": "QR code",
     "Draft discarded": "Brouillon abandonné",
     "Draft saved": "Brouillon enregistré",

web/src/locales/ja.ts

@@ -1193,6 +1193,8 @@ export const catalog: Catalog = {
     "Maximize": "最大化",
     "Full screen": "全画面",
     "Resize panes": "ペインの大きさを変更",
+    "Resize message list": "メール一覧の大きさを変更",
+    "Resize sidebar": "サイドバーの大きさを変更",
     "QR code": "QR コード",
     "Draft discarded": "下書きを破棄しました",
     "Draft saved": "下書きを保存しました",

web/src/locales/nl.ts

@@ -1181,6 +1181,8 @@ export const catalog: Catalog = {
     "Maximize": "Maximaliseren",
     "Full screen": "Volledig scherm",
     "Resize panes": "Vensterdelen verslepen",
+    "Resize message list": "Grootte van de berichtenlijst wijzigen",
+    "Resize sidebar": "Grootte van de zijbalk wijzigen",
     "QR code": "QR-code",
     "Draft discarded": "Concept weggegooid",
     "Draft saved": "Concept opgeslagen",

web/src/locales/pt-BR.ts

@@ -1188,6 +1188,8 @@ export const catalog: Catalog = {
     "Maximize": "Maximizar",
     "Full screen": "Tela cheia",
     "Resize panes": "Redimensionar os painéis",
+    "Resize message list": "Redimensionar a lista de mensagens",
+    "Resize sidebar": "Redimensionar a barra lateral",
     "QR code": "Código QR",
     "Draft discarded": "Rascunho descartado",
     "Draft saved": "Rascunho salvo",

web/src/locales/ru.ts

@@ -1187,6 +1187,8 @@ export const catalog: Catalog = {
     "Maximize": "Развернуть",
     "Full screen": "Во весь экран",
     "Resize panes": "Изменить размер панелей",
+    "Resize message list": "Изменить размер списка писем",
+    "Resize sidebar": "Изменить размер боковой панели",
     "QR code": "QR-код",
     "Draft discarded": "Черновик удалён",
     "Draft saved": "Черновик сохранён",

web/src/locales/uk.ts

@@ -1181,6 +1181,8 @@ export const catalog: Catalog = {
     "Maximize": "Розгорнути",
     "Full screen": "На весь екран",
     "Resize panes": "Змінити розмір панелей",
+    "Resize message list": "Змінити розмір списку листів",
+    "Resize sidebar": "Змінити розмір бічної панелі",
     "QR code": "QR-код",
     "Draft discarded": "Чернетку видалено",
     "Draft saved": "Чернетку збережено",

web/src/locales/zh-Hans.ts

@@ -1192,6 +1192,8 @@ export const catalog: Catalog = {
     "Maximize": "最大化",
     "Full screen": "全屏",
     "Resize panes": "调整窗格大小",
+    "Resize message list": "调整邮件列表大小",
+    "Resize sidebar": "调整侧边栏大小",
     "QR code": "二维码",
     "Draft discarded": "草稿已放弃",
     "Draft saved": "草稿已保存",