Usj to usfm

[kavitharaju]

This PR

• Implements one task in #217, USJ to USFM conversion, enabling round trippability
• Tests for the same
• Documentation in README and Python Notebook

:warning: The failing test cases are due to one testsuite file which needs a fix (\b should be \p)

How-To round trip

from usfm_grammar import USFMParser, Filter
from usfm_grammar import USFMParser, USFMGenerator

my_parser = USFMParser(input_usfm_str)
usj_obj = my_parser.to_usj()

my_generator = USFMGenerator()
my_generator.usj_to_usfm(usj_obj)
print(my_generator.usfm_string)

⚠️ There will be differences between first USFM and the generated one in 1. Spaces and lines 2. Default attributes will be given their names 3. Closing markers may be newly added

How-To remove unwanted markers from USFM

from usfm_grammar import USFMParser, Filter, USFMGenerator

my_parser = USFMParser(input_usfm_str)
usj_obj = my_parser.to_usj(include_markers=Filter.BCV+Filter.TEXT)

my_generator = USFMGenerator()
my_generator.usj_to_usfm(usj_obj)
print(my_generator.usfm_string)

[kavitharaju]

Changed the API as per the suggestion. This is how it is now

from usfm_grammar import USFMParser, Filter

my_parser = USFMParser(input_usfm_str)
usj_obj = my_parser.to_usj()

my_parser2 = USFMParser(from_usj=usj_obj)
print(my_parser2.usfm)