Fpdf2

Many thanks to [eumiro](https://github.com/py-pdf/fpdf2/pulls?q=is%3Apr+author%3Aeumiro) & [fbernhart](https://github.com/py-pdf/fpdf2/pulls?q=is%3Apr+author%3Aeumiro) for their contributions to make `fpdf2` code cleaner!
Added
- `FPDF.unbreakable` : a new method providing a context-manager in which automatic page breaks are disabled.
_cf._ https://py-pdf.github.io/fpdf2/PageBreaks.html
- `FPDF.epw` & `FPDF.eph` : new `property` methods to retrieve the **effective page width / height**, that is the page width / height minus its horizontal / vertical margins.
- `FPDF.image` now accepts also a `Pillow.Image.Image` as input
- `FPDF.multi_cell` parameters evolve in order to generate tables with multiline text in cells:
* its `ln` parameter now accepts a value of `3` that sets the new position to the right without altering vertical offset
* a new optional `max_line_height` parameter sets a maximum height of each sub-cell generated
- new documentation pages : how to add content to existing PDFs, HTML, links, tables, text styling & page breaks
- all PDF samples are now validated using 3 different PDF checkers
Fixed
- `FPDF.alias_nb_pages`: fixed this feature that was broken since v2.0.6
- `FPDF.set_font`: fixed a bug where calling it several times, with & without the same parameters,
prevented strings passed first to the text-rendering methods to be displayed.
Deprecated
- the `dest` parameter of `FPDF.output` method

Added
- new unit tests, a code formatter (`black`) and a linter (`pylint`) to improve code quality
- new boolean parameter `table_line_separators` for `write_html` & underlying `HTML2FPDF` constructor
Changed
- the documentation URL is now simply https://py-pdf.github.io/fpdf2/
Removed
- dropped support for external font definitions in `.font` Python files, that relied on a call to `exec`
Deprecated
- the `type` parameter of `FPDF.image` method
- the `infile` parameter of `Template` constructor
- the `dest` parameter of `Template.render` method

Added
* [Introducing a rect_clip() function](https://github.com/reingart/pyfpdf/pull/158)
* [Adding support for Contents alt text on Links](https://github.com/reingart/pyfpdf/pull/163)
Modified
* [Making FPDF.output() x100 time faster by using a bytearray buffer](https://github.com/reingart/pyfpdf/pull/164)
* Fix user's font path ([issue](https://github.com/reingart/pyfpdf/issues/166) [PR](https://github.com/py-pdf/fpdf2/pull/14))
Deprecated
* [Deprecating .rotate() and introducing .rotation() context manager](https://github.com/reingart/pyfpdf/pull/161)
Fixed
* [Fixing 159 issue with set_link + adding GitHub Actions pipeline & badges](https://github.com/reingart/pyfpdf/pull/160)
* `User defined path to font is ignored`
Removed
* non-necessary dependency on `numpy`
* support for Python 2

Added
* Python 3.9 is now supported

Added
* new specific exceptions: `FPDFException` & `FPDFPageFormatException`
* tests to increase line coverage in `image_parsing` module
* a test which uses most of the HTML features
Fixed
* handling of fonts by the HTML mixin (weight and style) - thanks `cgfrost`!

Fixed
* images centering - thanks `cgfrost`!
* added missing import statment for `urlopen` in `image_parsing` module
* changed urlopen import from `six` library to maintain python2 compatibility