Added support for manifest suggests and recommends fields as well as debscripts

[yuriusu22]

The following changes are:

1. Added an optional suggests and recommends dependency fields. You can now define the following entries in the JSON manifest file:

{
  ...
  "recommends": [],
  "suggests": []
  ...
}

Note: Unlike suggests, The recommends field will be automatically installed along with the depends field.

2. Added support for optional debscripts (see termux_step_create_debscripts in build step overrides for details).

Note: Debscripts will be automatically included and executed upon installation and removing. They should exist within the same directory as the manifest.

IMPORTANT: Might as well update the README file with these changes.

[ghost]

Thanks.