fix: mdc component completions

[adamdehaven]

Description

Fixes two issues with MDC component completions:

Component names

1. Start typing a component name ::accordio (i.e. a partial component name available in component-meta) but then press Escape to cancel auto-completion suggestions
2. Press Ctrl + Space to re-trigger completions, and notice only components that match the entire partial component name on the line are suggested.
3. When accepting a suggestion, the name isn't appended to the line, but instead properly replaces the entire component name to be correct.
4. When accepting a suggestion, if the component template (e.g. YAML block for props and slot content) is already injected into the template, it does not inject another props and slot template.

Component props

Same behavior described above for 1-3, but for MDC prop names within YAML blocks.

[adamdehaven]

@farnabaz @atinux I'm noticing there are no branch protections enabled for the repo (it looks like I can merge this pull request without a review, tests, etc.)

[atinux]

Just added @adamdehaven thank you!