Add integration tests for custom themes

Ensure file is executable for preprocessing to work

code exec on ctrl+e

Execute code block for supported languages (bash,go,ruby,python)

Merge pull request maaslalani#17 from maaslalani/stdin

Read slides from stdin

Merge pull request maaslalani#10 from meowgorithm/bump-libs

Bump Charm libraries and update deprecated method

go 1.16