Added <O extends SaxesOptions>

[biojet1]

my node typescript project got compilation error TS2344

tsc -d --sourcemap

Error: node_modules/saxes/saxes.d.ts(46,71): error TS2344: Type 'O' does not satisfy the constraint 'SaxesOptions'.
  Type 'O' is not assignable to type 'CommonOptions'.
Error: node_modules/saxes/saxes.d.ts(55,80): error TS2344: Type 'O' does not satisfy the constraint 'SaxesOptions'.
  Type 'O' is not assignable to type 'CommonOptions'.
Error: node_modules/saxes/saxes.d.ts(62,61): error TS2344: Type 'O' does not satisfy the constraint 'SaxesOptions'.
  Type 'O' is not assignable to type 'CommonOptions'.
Error: node_modules/saxes/saxes.d.ts(69,62): error TS2344: Type 'O' does not satisfy the constraint 'SaxesOptions'.
  Type 'O' is not assignable to type 'CommonOptions'.
Error: Process completed with exit code 2.

typescript version is

$ tsc --version
Version 4.8.3

with this pull request i can compile it now

i think typescript 4.8.3 became stricter

[tpluscode]

Could this be merged?

[rubensworks]

FYI, I also ran into this issue, and ended up forking the project (https://github.com/rubensworks/saxes), and releasing under @rubensworks/saxes.
Happy to dissolve my fork as soon as this PR gets merged.