Fix memory leak on BigImageViewer (#1067)

Leak found using LeakCanary. Steps:
1. Enable the LeakCanary dependency.
1. Open the app.
1. Open any post image, and go back.

According to `Piasy/BigImageViewer` documentation,
[Initialize section](https://github.com/Piasy/BigImageViewer/blob/9cc045e8146dc8833a487576745f17158bae4a4a/README.md#initialize),
the app context must be used to avoid memory leaks.

Leak trace:

```
2022-09-04 19:51:38.154 13332-13332/ml.docilealligator.infinityforreddit.debug D/LeakCanary:
    ┬───
    │ GC Root: Thread object
    │
    ├─ android.os.HandlerThread instance
    │    Leaking: NO (PathClassLoader↓ is not leaking)
    │    Thread name: 'LeakCanary-Heap-Dump'
    │    ↓ Thread.contextClassLoader
    ├─ dalvik.system.PathClassLoader instance
    │    Leaking: NO (BigImageViewer↓ is not leaking and A ClassLoader is never leaking)
    │    ↓ ClassLoader.runtimeInternalObjects
    ├─ java.lang.Object[] array
    │    Leaking: NO (BigImageViewer↓ is not leaking)
    │    ↓ Object[257]
    ├─ com.github.piasy.biv.BigImageViewer class
    │    Leaking: NO (a class is never leaking)
    │    ↓ static BigImageViewer.sInstance
    │                            ~~~~~~~~~
    ├─ com.github.piasy.biv.BigImageViewer instance
    │    Leaking: UNKNOWN
    │    Retaining 969.9 kB in 14812 objects
    │    ↓ BigImageViewer.mImageLoader
    │                     ~~~~~~~~~~~~
    ├─ com.github.piasy.biv.loader.glide.GlideImageLoader instance
    │    Leaking: UNKNOWN
    │    Retaining 969.9 kB in 14811 objects
    │    ↓ GlideImageLoader.mRequestManager
    │                       ~~~~~~~~~~~~~~~
    ├─ com.bumptech.glide.RequestManager instance
    │    Leaking: UNKNOWN
    │    Retaining 969.9 kB in 14808 objects
    │    context instance of ml.docilealligator.infinityforreddit.activities.ViewPostDetailActivity with mDestroyed = true
    │    ↓ RequestManager.context
    │                     ~~~~~~~
    ╰→ ml.docilealligator.infinityforreddit.activities.ViewPostDetailActivity instance
         Leaking: YES (ObjectWatcher was watching this because ml.docilealligator.infinityforreddit.activities.
         ViewPostDetailActivity received Activity#onDestroy() callback and Activity#mDestroyed is true)
         Retaining 966.2 kB in 14703 objects
         key = f69c74cc-521e-4f6c-b5c8-8f787e27df75
         watchDurationMillis = 5547
         retainedDurationMillis = 541
         mApplication instance of ml.docilealligator.infinityforreddit.Infinity
         mBase instance of androidx.appcompat.view.ContextThemeWrapper
```

0 files changed, 0 insertions, 0 deletions