fix the export of modules (#134)

depends on
- nushell/nushell#11157
- nushell/nupm#47
- #140
- #141

## description
as directory modules won't export the modules next to any `mod.nu`, this
PR adds `export module` calls to `nu-git-manager-sugar` and the tests,
making the source base compatible again with
nushell/nushell#11157 and
nushell/nupm#47.

pkgs/nu-git-manager-sugar/nu-git-manager-sugar/git/mod.nu

@@ -6,6 +6,8 @@ use ../completions/nu-complete.nu [
     GIT_QUERY_TABLES, GIT_STRATEGIES, git-query-tables, get-remotes, get-branches, get-strategies
 ]
 
+export module prompt.nu
+
 # get the commit hash of any revision
 #
 # ## Examples

pkgs/nu-git-manager-sugar/tests/mod.nu

@@ -3,6 +3,8 @@ use std assert
 use ../../../tests/common/import.nu ["assert imports"]
 use ../../../tests/common/setup.nu [get-random-test-dir]
 
+export module git.nu
+
 const MODULE = "nu-git-manager-sugar"
 
 export module imports {

pkgs/nu-git-manager/tests/mod.nu

@@ -20,6 +20,8 @@ use ../../../pkgs/nu-git-manager/nu-git-manager/fs/dir.nu [clean-empty-directori
 
 use ../../../tests/common/setup.nu [get-random-test-dir]
 
+export module gm.nu
+
 export module path {
     export def sanitization [] {
         assert equal ('\foo\bar' | path sanitize) "/foo/bar"

src/nu-git-manager-sugar/mod.nu

@@ -0,0 +1,3 @@
+export module extra.nu
+export module git
+export module github.nu