Remove Pkg as a dependency

In recent Julia versions Pkg is not in the sysimage and therefore it can
not be loaded "for free". Pkg was only used to conditionally activate
the documentation environment in `LiveServer.servedocs` so the loss of
functionality is basically non-existent -- it is easy enough to
configure the package environment before calling `LiveServer.servedocs`.

Timings for loading LiveServer on Julia 1.12:
```
julia> @time using LiveServer # this PR
  0.448249 seconds

julia> @time using LiveServer # master
  0.743163 seconds
```

Project.toml

@@ -7,7 +7,6 @@ version = "1.3.1"
 HTTP = "cd3eb016-35fb-5094-929b-558a96fad6f3"
 LoggingExtras = "e6f89c97-d47a-5376-807f-9c37f3926c36"
 MIMEs = "6c6e2e6c-3030-632d-7369-2d6c69616d65"
-Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Sockets = "6462fe0b-24de-5631-8697-dd941f90decc"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 

src/LiveServer.jl

@@ -1,6 +1,6 @@
 module LiveServer
 
-import Sockets, Pkg, MIMEs
+import Sockets, MIMEs
 using Base.Filesystem
 using Base.Threads: @spawn
 

src/utils.jl

@@ -184,8 +184,6 @@ subfolder `docs`.
 
 * `verbose=false`: boolean switch to make the server print information about
                    file changes and connections.
-* `doc_env=false`: a boolean switch to make the server start by activating the
-doc environment or not (i.e. the `Project.toml` in `docs/`).
 * `literate=nothing`: see `literate_dir`.
 * `literate_dir=nothing`: Path to a directory containing Literate scripts if
                           these are not simply under `docs/src`. 
@@ -271,7 +269,12 @@ function servedocs(;
     )
 
     # activate the doc environment if required
-    doc_env && Pkg.activate(joinpath(foldername, "Project.toml"))
+    if doc_env
+        msg = "The `doc_env` keyword argument is deprecated. Configure the environment " *
+            "before calling LiveServer.servedocs instead."
+        Base.depwarn(msg, :servedocs)
+        prev = deprecated_activate(joinpath(foldername, "Project.toml"))
+    end
 
     # trigger a first pass of Documenter (& possibly Literate)
     Main.include(abspath(path2makejl))
@@ -291,10 +294,18 @@ function servedocs(;
     )
 
     # when the serve loop is interrupted, de-activate the environment
-    doc_env && Pkg.activate()
+    if doc_env
+        deprecated_activate(prev)
+    end
     return
 end
 
+function deprecated_activate(path)
+    prev = Base.ACTIVE_PROJECT[]
+    Base.ACTIVE_PROJECT[] = path
+    return prev
+end
+
 
 #
 # Miscellaneous utils

test/Project.toml

@@ -2,7 +2,6 @@
 Crayons = "a8cc5b0e-0ffa-5ad4-8c14-923d3ee1735f"
 HTTP = "cd3eb016-35fb-5094-929b-558a96fad6f3"
 MIMEs = "6c6e2e6c-3030-632d-7369-2d6c69616d65"
-Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Sockets = "6462fe0b-24de-5631-8697-dd941f90decc"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"