Fix scap on windows

[kerosina]

While compiling for windows, I get the following errors:

error[E0053]: method `new` has an incompatible type for trait
  --> C:\Users\makedon\.cargo\registry\src\index.crates.io-6f17d22bba15001f\scap-0.0.7\src\capturer\engine\win\mod.rs:39:25
   |
39 |     fn new(flag_values: Self::Flags) -> Result<Self, Self::Error> {
   |                         ^^^^^^^^^^^ expected `windows_capture::capture::Context<FlagStruct>`, found `FlagStruct`
   |
   = note: expected signature `fn(windows_capture::capture::Context<FlagStruct>) -> Result<_, _>`
              found signature `fn(FlagStruct) -> Result<_, _>`
help: change the parameter type to match the trait
   |
39 |     fn new(flag_values: windows_capture::capture::Context<FlagStruct>) -> Result<Self, Self::Error> {
   |                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error[E0599]: no method named `as_raw_nopadding_buffer` found for struct `FrameBuffer` in the current scope
  --> C:\Users\makedon\.cargo\registry\src\index.crates.io-6f17d22bba15001f\scap-0.0.7\src\capturer\engine\win\mod.rs:65:61
   |
65 |                 let raw_frame_buffer = match cropped_buffer.as_raw_nopadding_buffer() {
   |                                                             ^^^^^^^^^^^^^^^^^^^^^^^
   |
help: there is a method `as_nopadding_buffer` with a similar name
   |
65 |                 let raw_frame_buffer = match cropped_buffer.as_nopadding_buffer() {
   |                                                             ~~~~~~~~~~~~~~~~~~~

This PR fixes both errors by following the compiler's suggestions (modifying the function to take a Context and using as_nopadding_buffer).