Prerelease does not Respect Default_Bump

[lazyBisa]

When having default_bump=minor I would expect a prerelease to do a minor update when creating the prerelease version. Currently it always does a patch update.

E.g.
latest release is 1.2.3, I would expect an execution of the action on a branch basing from that version, with parameters default_bump=minor and default_prerelease_bump=prerelease to generate the version 1.3.0-beta.0, since 1.3.0 is the version the final release will (most likely) be.
Instead, it currently generates the version 1.2.4-beta.0, which is a patch increase.

Another run on top should then do the correct prerelease update to create version 1.3.0-beta.1

I think adjustments need to address the code starting at

github-tag-action/src/action.ts

Line 155 in e923a61

if (isPrerelease && !bump) {

You could argue that this is a bug/feature of semver itself, but it really is relating to correctly interpreting default actions which is responsibility of this module, not semver.