feat(sidebar): can hide divider and footer

[pidupuis]

What kind of change does this PR introduce? (check one with "x")

• Bug fix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

---

Description

• Sidebar dividers can now be displayed or removed after each sidebar item.
• Footer can be hidden.

---

Verification steps

Update the sidebar configuration part by changing divider value for the different items.

[neoFelhz]

Maybe you can add missed icon configurations in _config.template.yml in this pull requeset,which was forgotten to add in pull #165

[pidupuis]

@neoFelhz Could you tell me which one are missing please?

[neoFelhz]

In _config.template.yml ,from line 109 to 127.
It should be:

# Sidebar Customize
sidebar:
    dropdown:
        Email Me:
            link: "#"
            icon: email
    homepage:
        use: true
        icon: home
    archives:
        use: true
        icon: inbox
    categories:
        use: false
        icon: chrome_reader_mode
    pages:
        #About:
            #link: "/about"
            #icon: person

I missed configure the three default icons。

[pidupuis]

@neoFelhz Oh ok sure :)