Move old harfbuzz.org content to README.md

Copied from:

  https://web.archive.org/web/20191221151847/https://freedesktop.org/wiki/Software/HarfBuzz/

Edited lightly trying to merge it with existing README.md content and
remove grossly outdated bits. Might still need more editing.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1919

README.md

@@ -6,7 +6,12 @@
 [![Codecov Code Coverage](https://codecov.io/gh/harfbuzz/harfbuzz/branch/main/graph/badge.svg)](https://codecov.io/gh/harfbuzz/harfbuzz)
 [![Packaging status](https://repology.org/badge/tiny-repos/harfbuzz.svg)](https://repology.org/project/harfbuzz/versions)
 
-This is HarfBuzz, a text shaping library.
+# HarfBuzz
+
+HarfBuzz is a text shaping engine. It primarily supports [OpenType][1], but also
+[Apple Advanced Typography][2]. HarfBuzz is used in Android, Chrome,
+ChromeOS, Firefox, GNOME, GTK+, KDE, LibreOffice, OpenJDK, PlayStation, Qt,
+XeTeX, and other places.
 
 For bug reports, mailing list, and other information please visit:
 
@@ -14,14 +19,51 @@ For bug reports, mailing list, and other information please visit:
 
 For license information, see [COPYING](COPYING).
 
+## Documentation
+
+For user manual as well as API documentation, check: https://harfbuzz.github.io
+
+## Download
+
+For tarball releases of HarfBuzz, look [here][3]. At the same place you
+will also find Win32/Win64 binary bundles that include libharfbuzz DLL,
+hb-view.exe, hb-shape.exe, and all dependencies.
+
+The canonical source tree is available on [github][4].
+
+The API that comes with `hb.h` will not change incompatibly. Other, peripheral,
+headers are more likely to go through minor modifications, but again, we do our
+best to never change API in an incompatible way. We will never break the ABI.
+
+If you are not sure whether Pango or HarfBuzz is right for you, read [Pango vs
+HarfBuzz][5].
+
+## Development
+
 For build information, see [BUILD.md](BUILD.md).
 
 For custom configurations, see [CONFIG.md](CONFIG.md).
 
 For test execution, see [TESTING.md](TESTING.md).
 
-Documentation: https://harfbuzz.github.io
+To get a better idea of where HarfBuzz stands in the text rendering stack you
+may want to read [State of Text Rendering][6], though, that document is many
+years old. Here are a few presentation slides about HarfBuzz at the
+Internationalization and Unicode Conference over the years:
 
+*   November 2014, [Unicode, OpenType, and HarfBuzz: Closing the Circle][7],
+*   October 2012, [HarfBuzz, The Free and Open Text Shaping Engine][8],
+*   October 2009, [HarfBuzz: the Free and Open Shaping Engine][9].
+
+Both development and user support discussion around HarfBuzz happens on the
+[github][4].
+
+To report bugs or submit patches please use [github][4] issues and
+pull-requests.
+
+For a comparison of old vs new HarfBuzz memory consumption see [this][10].
+
+<!--See past and upcoming [HarfBuzz Hackfests](https://freedesktop.org/wiki/Software/HarfBuzz/Hackfests/)!-->
 
 <details>
   <summary>Packaging status of HarfBuzz</summary>
@@ -29,3 +71,14 @@ Documentation: https://harfbuzz.github.io
 [![Packaging status](https://repology.org/badge/vertical-allrepos/harfbuzz.svg?header=harfbuzz)](https://repology.org/project/harfbuzz/versions)
 
 </details>
+
+[1]: https://docs.microsoft.com/en-us/typography/opentype/spec/
+[2]: https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6AATIntro.html
+[3]: https://github.com/harfbuzz/harfbuzz/releases
+[4]: https://github.com/harfbuzz/harfbuzz
+[5]: http://mces.blogspot.com/2009/11/pango-vs-harfbuzz.html
+[6]: http://behdad.org/text/
+[7]: https://goo.gl/FSIQuC
+[8]: https://goo.gl/2wSRu
+[9]: http://behdad.org/download/Presentations/slippy/harfbuzz_slides.pdf
+[10]: https://goo.gl/woyty