Fix around logo (#449)

* Use relative path in README

* update logo.png for transparent background

* add favicon.ico

* update make.jl for favicon

Author: hyrodium

README.md

@@ -1,4 +1,4 @@
-<h1><img src="https://raw.githubusercontent.com/JuliaPy/PythonCall.jl/main/docs/src/assets/logo.png" alt="PythonCall.jl logo" style="width: 100px;"><br>PythonCall &amp;&nbsp;JuliaCall</h1>
+<h1><img src="docs/src/assets/logo.png" alt="PythonCall.jl logo" style="width: 100px;"><br>PythonCall &amp;&nbsp;JuliaCall</h1>
 
 [![Project Status: Active – The project has reached a stable, usable state and is being actively developed.](https://www.repostatus.org/badges/latest/active.svg)](https://www.repostatus.org/#active)
 [![Stable Documentation](https://img.shields.io/badge/docs-stable-blue.svg)](https://juliapy.github.io/PythonCall.jl/stable)

docs/make.jl

@@ -5,6 +5,9 @@ include("customdocs.jl")
 makedocs(
     sitename = "PythonCall & JuliaCall",
     modules = [PythonCall],
+    format = Documenter.HTML(
+        assets = ["assets/favicon.ico"],
+    ),
     warnonly = [:missing_docs], # avoid raising error when docs are missing
     pages = [
         "Home" => "index.md",