Docs: Add missing defaults to ISuggestOptions

[michaelboyles]

When browsing the online type docs, it's annoying that only some of the options describe the default value.

This change adds defaults to all the options. There were also 2 options with incorrect defaults:

insertMode - the default was listed as false, which is not a valid value. The default is 'insert'.

snippetsPreventQuickSuggestions - the default was listed true, but is actually false

[michaelboyles]

@microsoft-github-policy-service agree