Merge the 2 gitsigns.nvim configs

[oriori1703]

I think it can be confusing for new users to have gitsigns configured in 2 places.

I'm still undecided if the merged config be in init.lua or gitsigns.lua.
In the latter, gitsigns would be disabled entirely by default, because everything outside of init.lua is optional and disabled by default.
I'm leaning towards the former because I think it is useful to for new users to know which lines they changed (especially if they didn't mean to because they are still new to neovim).

Another option is to enable the keymaps by default, which further implies that it should be in init.lua.

Anyone has opinions on this?

[dam9000]

My vote is to enable the keymaps by default, but that's just me.
If they remain commented out I would suggest to use block instead of line comment, so:

--[[
...
--]]

[nathanzeng]

Note: closes #1926

[nathanzeng]

I vote enable by default. The other places in kickstart that there is commented out code, it feels much more optional or debatable. People almost certainly want these keymaps.

They might want the keys to be different, which is why they can change it.