Update prop type & documentation for HistoryVisibleBanner and VM. (#31545)

* docs: Update documentation for HistoryVisibleBanner and VM.

* docs: Improve documentation for `HistoryVisibleBanner`, second pass.

* docs: Move documentation to prop types over FC.

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* fix: Simplify type for `HistoryVisibleBannerViewModel` `threadId`.

* docs: Apply suggestions from code review

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

test/unit-tests/components/viewmodels/composer/HistoryVisibleBannerViewModel-test.tsx

@@ -54,7 +54,7 @@ describe("HistoryVisibleBannerViewModel", () => {
     });
 
     it("should not show the banner in unencrypted rooms", () => {
-        const vm = new HistoryVisibleBannerViewModel({ room });
+        const vm = new HistoryVisibleBannerViewModel({ room, threadId: null });
         expect(vm.getSnapshot().visible).toBe(false);
     });
 
@@ -76,7 +76,7 @@ describe("HistoryVisibleBannerViewModel", () => {
             }),
         ]);
 
-        const vm = new HistoryVisibleBannerViewModel({ room });
+        const vm = new HistoryVisibleBannerViewModel({ room, threadId: null });
         expect(vm.getSnapshot().visible).toBe(false);
     });
 
@@ -99,7 +99,7 @@ describe("HistoryVisibleBannerViewModel", () => {
             }),
         ]);
 
-        const vm = new HistoryVisibleBannerViewModel({ room });
+        const vm = new HistoryVisibleBannerViewModel({ room, threadId: null });
         expect(vm.getSnapshot().visible).toBe(false);
         vm.dispose();
     });
@@ -145,7 +145,7 @@ describe("HistoryVisibleBannerViewModel", () => {
             }),
         ]);
 
-        const vm = new HistoryVisibleBannerViewModel({ room });
+        const vm = new HistoryVisibleBannerViewModel({ room, threadId: null });
         expect(vm.getSnapshot().visible).toBe(true);
         await vm.onClose();
         expect(vm.getSnapshot().visible).toBe(false);