This task is suitable for day to day docs authoring.
This task cuts corners, which makes it much faster than a full `yarn docs`
run but it does not produce completely valid output.
In general this isgood enough for authors to see their changes as they make them.
The task is triggered by a call to
```
yarn docs-watch
```
This sets up watchers on the `aio/contents` and `packages` folders.
Any changes to files below these folders new doc generation run to start.
The input to the generation is confined to a collection of files related
to the changed file. For example:
* a change to a file in `aio/content/marketing` will generate all the
marketing files.
* a change to a file in `aio/content/tutorial` or `aio/examples/toh-*`
will generate all the tutorial files (and their embedded examples).
* a change to a file in `aio/guide` or `aio/examples` (but not a `toh-`
example) will generate the appropriate guide and its embedded examples
* a change to a file in `packages` or `packages/examples` will generate
the appropriate API doc and its embedded examples.
Be aware that the mapping between docs and its examples are based on doc file
and example folder structure being equivalent. Sometimes a doc will reference
an example in a different folder, in which case the generated doc will be
inaccurate. Mostly this is not a big problem.
All the docs related files (docs-app, doc-gen, content, etc)
are now to be found inside the `/aio` folder.
The related gulp tasks have been moved from the top level
gulp file to a new one inside the `/aio` folder.
The structure of the `/aio` folder now looks like:
```
/aio/
build/ # gulp tasks
content/ #MARKDOWN FILES for devguides, cheatsheet, etc
devguides/
cheatsheets/
transforms/ #dgeni packages, templates, etc
src/
app/
assets/
content/ #HTML + JSON build artifacts produced by dgeni from /aio/content.
#This dir is .gitignored-ed
e2e/ #protractor tests for the doc viewer app
node_modules/ #dependencies for both the doc viewer builds and the dgeni stuff
#This dir is .gitignored-ed
gulpfile.js #Tasks for generating docs and building & deploying the doc viewer
```
Closes#14361
Ward Bell
Jesus Rodriguez
Peter Bacon Darwin