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.

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.

Allow the keybindings to have an effect in the "Try here" text field.

Incompatible APIs were used in the custom layouts and the extra keys
options.

Add @TargetApi annotations to help catch similar issues in the future
with the help of 'gradle lint'.