feat(colorscheme): Add Alabaster colorscheme

Author: nullcopy

lua/astrocommunity/colorscheme/alabaster/README.md

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+# aurora
+
+Minimalist color scheme for Sublime Text 3
+
+**Repository:** <https://github.com/p00f/alabaster.nvim>
+
+```vim
+" Vim Script
+colorscheme alabaster
+```

lua/astrocommunity/colorscheme/alabaster/init.lua

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+return { "p00f/alabaster.nvim", lazy = true }