Combine combining characters (optionally) in 'as_bm_list.character()'

[trevorld]

Any character whose "Canonical_Combining_Class" property is above zero is a combining character:

Unicode::u_char_property("U+0333", "Canonical_Combining_Class")
220

A bit of documentation about the property: https://www.gnu.org/software/libunistring/manual/html_node/Canonical-combining-class.html

We should probably just support applying bm_overlay() to the base character and the combining characters.

[trevorld]

Would also be nice to have an option to combine (U)CSUR glyphs. Unifont has such a list of such.

[trevorld]

• Supports this in as_bm_bitmap.character()
• Leave as_bm_list.character() a bit more low-level for now (for now can chain with bm_compose())