Introduce GLM Specific Diagnostic Plots

[macamiri]

3 main additions to ggDoE:

1. Add glm_diagnostic_plots() function, which returns 9 diagnostic plots for Generalized Linear Models. Similar to existing diagnostic_plots() function with slight modifications to specifically accommodate GLMs.
2. Create simple hexsticker/logo for package. Image is based on the lambda_plot() function output in the vignette.
3. Update vignette to (a) include the glm_diagnostic_plots examples, and (b) allow viewers to click on the list of content at the top and jump to section.

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[toledo60]

Thank you for the great start in the glm diagnostics plots, I'll clean up some bugs/errors from here.
Make sure you run devtools::check() and you get '0 errors 0 warning 0 notes'
Luckily, they were small issues that I can quickly fix.