Add withSiteTitle params

[Lruihao]

Hi @Lruihao , your template is really powerful and saved me many days of work, thanks again.

I just discovered my website name is contained in the title of all my pages (under "head" HTML tag), and I wonder if this could be an issue for indexing. I'm a bit uncomfortable with SEO and I would like to clarify why only 30% of my website is indexed on Google.

Is it intentional to replicate "name" value (located under "params.header.title") into all pages title?
Can't it slow / block the indexing process from Google?

Originally posted by @Kapusch in #392

[Lruihao]

add params.withSiteTitle and params.titleDelimiter to support.

[params]
  # ...
  # FixIt 0.3.0 | NEW whether to add site title to the title of every page
  # remember to set up your site title in `hugo.toml` (e.g. title = "title")
  withSiteTitle = true
  # FixIt 0.3.0 | NEW title delimiter when the site title is be added to the title of every page
  titleDelimiter = "-"