chore(CODEOWNERS): prefix directories with root slash (gnolang#1573)

Pull request gnolang#1572 marks the codeowner as @moul, in spite of what the
configuration might suggest to a human reader.

[Reading through GitHub's
docs](https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners#example-of-a-codeowners-file),
this seems to come from the fact that if directories are not prefixed
with a `/`, they are considered as applying to all files or directories
with that name. (ie. `foo` matches `/foo` but also `/src/foo`).

I've added `/` to all directories in CODEOWNERS to fix this.

.github/CODEOWNERS

@@ -1,67 +1,67 @@
 # CODEOWNERS: https://help.github.com/articles/about-codeowners/
 
 # Primary repo maintainers.
-*                            @gnolang/tech-staff
+*                             @gnolang/tech-staff
 
 # Tendermint2 (Gno version).
-tm2/*                        @gnolang/tech-staff
-tm2/pkg                      @jaekwon @piux2 @moul @zivkovicmilos
-tm2/pkg/crypto               @jaekwon @moul @gnolang/security
+/tm2/*                        @gnolang/tech-staff
+/tm2/pkg                      @jaekwon @piux2 @moul @zivkovicmilos
+/tm2/pkg/crypto               @jaekwon @moul @gnolang/security
 # TODO: add per package exceptions
 # ...
 
 # Docs & Content.
-docs/                        @gnolang/devrels
-misc/docusaurus/             @gnolang/devrels
-README.md                    @gnolang/devrels
-.gitpod.yml                  @gnolang/devrels
+/docs/                        @gnolang/devrels
+/misc/docusaurus/             @gnolang/devrels
+/README.md                    @gnolang/devrels
+/.gitpod.yml                  @gnolang/devrels
 
 # Gno examples and default contracts.
-examples/                    @gnolang/tech-staff @gnolang/devrels
-examples/gno.land/r/gnoland/ @moul
-examples/gno.land/r/gov/     @moul
-examples/gno.land/r/sys/     @moul
-examples/gno.land/r/worx/    @moul
-examples/gno.land/r/x        @gnolang/devrels
+/examples/                    @gnolang/tech-staff @gnolang/devrels
+/examples/gno.land/r/gnoland/ @moul
+/examples/gno.land/r/gov/     @moul
+/examples/gno.land/r/sys/     @moul
+/examples/gno.land/r/worx/    @moul
+/examples/gno.land/r/x        @gnolang/devrels
 # TODO: add people from the community here.
-examples/gno.land/r/jaekwon/ @jaekwon
-examples/gno.land/r/manfred/ @moul
+/examples/gno.land/r/jaekwon/ @jaekwon
+/examples/gno.land/r/manfred/ @moul
 
 # Gno.land.
-gno.land/                    @moul
-gno.land/pkg/integration     @gfanton
+/gno.land/                    @moul
+/gno.land/pkg/integration     @gfanton
 #...
 
 # GnoVM/Gnolang.
-gnovm/                       @gnolang/tech-staff
-gnovm/stdlibs                @jaekwon @thehowl
-gnovm/tests                  @jaekwon @piux2 @thehowl @moul
-gnovm/cmd/gno                @jaekwon @thehowl @harry-hov @moul
-gnovm/pkg/gnolang            @jaekwon @piux2 @thehowl @moul
-gnovm/pkg/doc                @thehowl
-gnovm/pkg/gnomod             @harry-hov
-gnovm/pkg/integration        @gfanton
-#gnovm/pkg/gnoenv
-#gnovm/pkg/repl
+/gnovm/                       @gnolang/tech-staff
+/gnovm/stdlibs                @jaekwon @thehowl
+/gnovm/tests                  @jaekwon @piux2 @thehowl @moul
+/gnovm/cmd/gno                @jaekwon @thehowl @harry-hov @moul
+/gnovm/pkg/gnolang            @jaekwon @piux2 @thehowl @moul
+/gnovm/pkg/doc                @thehowl
+/gnovm/pkg/gnomod             @harry-hov
+/gnovm/pkg/integration        @gfanton
+#/gnovm/pkg/gnoenv
+#/gnovm/pkg/repl
 
 # Contribs
-contribs/                    @gnolang/tech-staff
-contribs/gnodev              @gfanton
-contribs/gnokeykc            @moul
-contribs/gnomd               @moul
+/contribs/                    @gnolang/tech-staff
+/contribs/gnodev              @gfanton
+/contribs/gnokeykc            @moul
+/contribs/gnomd               @moul
 #...
 
 # Misc
-misc/                        @gnolang/tech-staff
-misc/loop                    @moul @gnolang/devops
-misc/deployments             @moul @gnolang/devops
-misc/genstd                  @thehowl
+/misc/                        @gnolang/tech-staff
+/misc/loop                    @moul @gnolang/devops
+/misc/deployments             @moul @gnolang/devops
+/misc/genstd                  @thehowl
 #...
 
 # Special files.
-PLAN.md                      @jaekwon @moul
-PHILOSOPHY.md                @jaekwon
-CONTRIBUTING.md              @jaekwon @moul @gnolang/tech-staff
-LICENSE.md                   @jaekwon
-.github/                     @moul @gnolang/tech-staff
-.github/CODEOWNERS           @jaekwon @moul
+/PLAN.md                      @jaekwon @moul
+/PHILOSOPHY.md                @jaekwon
+/CONTRIBUTING.md              @jaekwon @moul @gnolang/tech-staff
+/LICENSE.md                   @jaekwon
+/.github/                     @moul @gnolang/tech-staff
+/.github/CODEOWNERS           @jaekwon @moul