Add markers

[mrharpo]

Create a Marker component.

Each marker will have a time property and an editable text description.

class Marker() {
  constructor(vnode) {
    this.time = vnode.attrs.time
    this.text = vnode.attrs.text
  }
  view(vnode) {
    return m('.marker', {time: this.time}, [
      m('.marker_text', this.text)
    ])
  }
}

Markers will be instantiated on clips.
src/Clip.js

m.request('/markers/' + this.filename).then( (m) => {
  this.markers = m
}

marker information, is pulled from api:

@app.get('/markers/{filename}')
def get_markers(filename: str):
    # get list of markers
    return markers