There is a missing import within the `uint8-to-base64` javascript
package which assumes that `atob` and `btoa` are present and exported
instead of using the `window.atob` and `window.btoa` functions. This
previously worked but as far as I can see things have become more strict
and this no longer works.

The dependency is small and I do not believe that we gain much from
having this code as an external dependency. I think instead we should
just consume this dependency and bring the code directly into Gitea
itself - the code is itself just some standard incantation for creating
base64 arrays in javascript.

Therefore this PR simply removes the dependency on `uint8-to-base64` and
rewrites the functions used in it.

Fix go-gitea#22507

Signed-off-by: Andrew Thornton <[email protected]>

Co-authored-by: delvh <[email protected]>

Signed-off-by: Andrew Thornton <[email protected]>

…tob-on-window

Signed-off-by: Andrew Thornton <[email protected]>

Signed-off-by: Andrew Thornton <[email protected]>