Default mode for `git reset`

[AdrienMatricon]

• The git reset command can be performed with various modes (--soft, --mixed, --hard, --merge, --keep)
• Trying to perform a reset through sourcegit opens a pop-up asking to choose a mode among those
• The default choice in the pop-up (--soft) does not match the default mode in the git command line (--mixed)
• I assume that this is not on purpose (though if there is an actual demand for changing the default to --soft, I suggest adding a field in the Preferences menu instead to let the users tune the behavior)

[love-linger]

Now the default reset mode has been changed to --mixed, you can download the latest build from Github Action.