Support option "--output" for command "get chaos-experiments"

[OhRaph]

The value of flag "--output" isn't evaluated when using command "get chaos-experiments".

This is the behavior we have:

litmusctl get chaos-experiments --project-id "066950eb-0914-49b1-8bda-b652f86cb7ab" -o="yaml"
Use the arrow keys to navigate: ↓ ↑ → ← 
? Select an output format: 
  ▸ table
    json
    yaml

Moreover:

• the value "table" isn't mentioned in the doc
• there is no guard to check the validity of the value provided in option "--output"

I propose to add these changes.

Note: I'm not familiar with Go language. The code I provide is mainly derived from existing one, and I've search on Internet to achieve some part I could do by myself.

Please feel free to improve it as you want.
By advance, sorry for the possible mistakes I've made.

[OhRaph]

I can see that this PR is already addressing the non evaluation of flag "--output".
But it's doesn't ensure that the value provided by argument is valid.

[Nageshbansal]

@shivam-Purohit could you PTAL

[shivam-Purohit]

we could also merge the if statements into one to get rid of repeating promptui code. if == "" &&
Maybe something like input a valid output format