Trac #30540: Add package phitigra: Graph editor that works with Jupyter

This ticket is about providing the graph editor
https://pypi.org/project/phitigra, which works in Jupyter (Jupyter
Notebook and !JupyterLab).

This is part of

- #29889: Metaticket: Jupyter improvements for things that were in
sagenb

Related:

- [https://stackoverflow.com/q/63803031 Stack Overflow question
63803031: Graph drawing tool that gives graph6 code]

- [https://trac.sagemath.org/query?order=id&desc=1&summary=~graph_editor
&summary=~graph+editor&or&description=~graph_editor&description=~graph+e
ditor Sage Trac tickets about graph editor]

- [https://github.com/sagemath/sagenb/tree/b360a0172e15501fb0163d02dce71
3a561fee2af/sagenb/data/graph_editor graph_editor source code in
archived sagenb code repository]

URL: https://trac.sagemath.org/30540
Reported by: slelievre
Ticket author(s): Matthias Koeppe
Reviewer(s): David Coudert

Author: Release Manager

build/pkgs/phitigra/SPKG.rst

@@ -0,0 +1,16 @@
+phitigra: A graph editor for SageMath/Jupyter
+=============================================
+
+Description
+-----------
+
+A graph editor for SageMath/Jupyter
+
+License
+-------
+
+Upstream Contact
+----------------
+
+https://pypi.org/project/phitigra/
+

build/pkgs/phitigra/dependencies

@@ -0,0 +1,5 @@
+$(PYTHON) ipywidgets pillow numpy | $(PYTHON_TOOLCHAIN)
+
+These dependencies include the install-requires of ipycanvas.
+----------
+All lines of this file are ignored except the first.

build/pkgs/phitigra/requirements.txt

@@ -0,0 +1 @@
+phitigra

build/pkgs/phitigra/type

@@ -0,0 +1 @@
+optional