feat: new "subword" text object

[nikitarevenco]

this is a new text object which operates on parts of snake_case, kebab-case, camelCase, PascalCase and /path/case

It's a subword, so it's mapped to s

Below is a table showcasing various use-cases of this new text object. * is just an indicator for where the cursor is and is not part of the text

mis selects an inner subword, mas selects an outer subword which includes the delimiter. d deletes the selection.

before	inner (misd)	outer (masd
snake_case_lon*g	snake_case_	snake_case
snake_ca*se_long	snake__long	snake_long
snake__ca*se__longier	snake____long	snake__long
snake__case__long*ier	snake__case__	snake__case
c*amelCaseLong	camelCase	CaseLong
camelCa*seLong	camelLong	camelLong
camelCAseNotRE*Ally	camelCAseNot	camelCAseNot
camelCA*seNotREAlly	camelNotREAlly	camelNotREAlly
snake_Ri*ding_a_Camel_Case	snake__a_Camel_Case	snake_a_CamelCase
sn*ake_Riding_a_Camel_Case	_Riding_a_Camel_Case	Riding_a_Camel_Case
P*ascalCaseLong	CaseLong	CaseLong
tast*y-kebab-case	-kebab-case	kebab-case
tasty-kebi*ab-case	tasty--case	tasty-case
path/som*ewhere/../case	path//../case	path/../case
../.*./path/case/	..//path/case	../path/case
../path/case/som*ewhere	../path/case/	../path/case