Fold dependencies into vendor directory

[dmarcos]

buffer, debug, deep-assign.

Goal is to clean up all external dependencies so we can eventually enable no-build A-Frame

[vincentfretin]

Note buffer is only used for load-bmfont/three-bmfont-text.

[dmarcos]

if we move text to troika it seems we can get rid of three of the dependencies

[dmarcos]

would be cool to have just three as external dependency