This adds dictionary-based spell checking to the keyboard. The keyboard looks at the word being typed and matches it against a dictionary to either complete the rest of the word or find alternative spellings.

The core of this feature is implemented in cdict, which is included as a
submodule in vendor/cidct.

Cdict is developped at https://github.com/Julow/cdict
The dictionaries are hosted at https://github.com/Julow/Unexpected-Keyboard-dictionaries/
The wordlists used to build the dictionaries are the same ones used by
HeliBoard from https://codeberg.org/Helium314/aosp-dictionaries

- Add an activity accessible from the launcher app that lists available
  dictionaries with a download button.
  The DictionaryListView view shows the list of available dictionaries and
  handles downloading and installing them.

- The Dictionaries class manages installed dictionaries. Dictionaries are
  installed as individual files into the app's private directory.

- Available dictionaries are listed in dictionaries.xml, which is generated
  when building Unexpected-Keyboard-dictionaries.
  method.xml mentions the dictionary name for each locales.

The fade-in caused the trace to be hidden when animations are disabled.

Replace the short video with an animated vector image that shows the
swipe gesture.

This is much lighter and reliable than the mp4 video, which failed to
play on many devices.

Source for the image of the key is in inkscape SVG format in srcs/res
and is converted to an android drawable when needed. The swipe animation
is hand-written.

This adds the clipboard pane, which allows to save an arbitrary number of
clipboards and to paste them later. The key can be disabled in settings.

Checking the "Recently copied text" checkbox will cause the keyboard to keep a
temporary history of copied text. This history can only contain 3 elements
which expire after 5 minutes.
If this is unchecked, no history is collected.

History entries can be pinned into the persisted list of pins.

Existing icons are kept for API < 26.

This was a half-finished feature:
- Dangerous when typing passwords
- Caused crash on some devices
- Ugly (on its own but also blinking when sliding and not fixed in size)