Rate under the pointer, filter a star range, and name Help as help

Rating keys in the grid follow darktable's rule: with the pointer over a
photograph outside the selection, 0-5, P, X and U judge that photograph
alone; over one inside it, the whole selection, as before; off the grid,
the selection. The hover is cleared when the grid scrolls, so a key after
a wheel turn cannot judge whatever used to be under the pointer.

Holding F and tapping digits filters by stars: one digit for exactly
that many, two for everything between them, F alone to show every
rating again. The filter gains a ceiling to do it (`max_rating`, one
BETWEEN in the query). The place record carries it, and a record from an
older build reads as having none. The star chips light across a capped
range and the bar says "2-3★ only" beside them.

The grid also takes Ctrl+E and Ctrl+Shift+E for the selection, Ctrl+V to
paste onto it and Ctrl+A to select all. The "Gestures" button is now
"Help", its sheet "Controls and shortcuts", and F1 opens it.

ui/dr-ui/src/gesture_book.rs

@@ -274,6 +274,27 @@ pub const GESTURES: &[Gesture] = &[
         pointer: "Open the People chip on the filter bar, click each name, then switch the chip beside them to \"all of them\"",
         keys: "",
     },
+    Gesture {
+        title: "Export the selection as the last export was",
+        section: "Library grid",
+        touch: "Select them, then Export in the selection bar",
+        pointer: "Select them, then Export in the selection bar",
+        keys: "Ctrl+Shift+E, or Ctrl+E to see the export settings first",
+    },
+    Gesture {
+        title: "Paste copied settings onto the selection",
+        section: "Library grid",
+        touch: "Select them, then \"Paste to N\" in the selection bar",
+        pointer: "Select them, then \"Paste to N\"",
+        keys: "Ctrl+V",
+    },
+    Gesture {
+        title: "Show only photographs with some number of stars",
+        section: "Library grid",
+        touch: "Tap a star chip in the filter bar",
+        pointer: "Click a star chip in the filter bar",
+        keys: "Hold F and tap a digit for exactly that many stars, or two digits for everything between them; tap F alone to show every rating again",
+    },
     Gesture {
         title: "Resize the thumbnails",
         section: "Library grid",
@@ -300,7 +321,7 @@ pub const GESTURES: &[Gesture] = &[
         section: "Library grid",
         touch: "Tap a star on the cell",
         pointer: "Hover the cell, then click a star",
-        keys: "0 to 5 on the selection",
+        keys: "0 to 5 with the pointer over it, or on the selection",
     },
     Gesture {
         title: "Choose the frame a folded burst shows",
@@ -321,7 +342,7 @@ pub const GESTURES: &[Gesture] = &[
         section: "Library grid",
         touch: "While selecting, press \"Select all\"",
         pointer: "While selecting, press \"Select all\"",
-        keys: "",
+        keys: "Ctrl+A",
     },
     Gesture {
         title: "Take photographs out of a collection",