Display available tutorials

[schloerke]

Fixes #224
Fixes #223

learnr::available_tutorials()
#> Available tutorials:
#> * grader
#>   - grading-demo   : "Grading demo"
#>   - recording-demo : "Recording demo"
#>   - scoping-rules  : "What do exercise chunks have access to?"
#>   - setup-rules    : "learnr Setup Rules v 0.9.2"
#>   - solutions-demo : "Solutions demo"
#> * learnr
#>   - hello         : "Hello, Tutorial!"
#>   - question_type : "Question Types in Learnr"
#>   - slidy         : "Slidly demo"

learnr::available_tutorials("learnr")
#> Available tutorials:
#> * learnr
#>   - hello         : "Hello, Tutorial!"
#>   - question_type : "Question Types in Learnr"
#>   - slidy         : "Slidly demo"

learnr::run_tutorial()
#> Available tutorials:
#> * grader
#>   - grading-demo   : "Grading demo"
#>   - recording-demo : "Recording demo"
#>   - scoping-rules  : "What do exercise chunks have access to?"
#>   - setup-rules    : "learnr Setup Rules v 0.9.2"
#>   - solutions-demo : "Solutions demo"
#> * learnr
#>   - hello         : "Hello, Tutorial!"
#>   - question_type : "Question Types in Learnr"
#>   - slidy         : "Slidly demo"

learnr::run_tutorial(package = "learnr")
#> Available tutorials:
#> * learnr
#>   - hello         : "Hello, Tutorial!"
#>   - question_type : "Question Types in Learnr"
#>   - slidy         : "Slidly demo"

learnr::run_tutorial("not found")
#> Error: `package` must be provided if `name` is provided.

learnr::run_tutorial("not found", package = "learnr")
#> Error: Tutorial "not found" was not found in the "learnr" package.
#> Available tutorials:
#> * learnr
#>   - hello         : "Hello, Tutorial!"
#>   - question_type : "Question Types in Learnr"
#>   - slidy         : "Slidly demo"

^{Created on 2019-05-29 by the reprex package (v0.2.1)}

[wch]

May want to use adist to find the closest match, and say something like "Did you mean <closest match>?"