Added example_methods configuration option

[mskog]

Adds the example_methods to define your own example methods.

Fixes #5

Test guide

Install a local version of the gem in a project that uses solargraph and rspec.

Configure rspec in your .solargraph.yml configuration file like so

rspec:
  example_methods:
    - my_it

Open a spec file and add something like this:

  describe "something" do
    let(:foobar){"hello"}

    my_it do
      expect(foobar).to eq "hello"
    end

    it do
      expect(foobar).to eq "hello"
    end
  end

The behavior should be equivalent. Go-to-definition etc should work like expected.

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[lekemula]

@mskog Thanks for the great suggestion and for putting up this PR! 🙏 It looks great.

I'll give it a quick test over the weekend and merge it right afterward.

[lekemula]

@mskog tested it locally and it worked as expected :)

Great work! Merging and cutting a new version shortly after. 🚀