more items that should not be added to repo

[prjemian]

Today, I found these uncommitted items in my local clone of the definitions repository:

(bluesky_2022_1) prjemian@zap:~/.../NeXus/definitions$ git status
On branch more-ignore-items
Untracked files:
  (use "git add <file>..." to include in what will be committed)
	manual/source/classes/applications/canSAS/
	manual/source/classes/applications/index.rst
	manual/source/classes/base_classes/index.rst
	manual/source/classes/contributed_definitions/container/
	manual/source/classes/contributed_definitions/index.rst

[prjemian]

Since these look like work-product of a build of the documentation, they should be added to the /.gitignore file. This PR does that:

(bluesky_2022_1) prjemian@zap:~/.../NeXus/definitions$ git status
On branch more-ignore-items
Your branch is up to date with 'origin/more-ignore-items'.

nothing to commit, working tree clean

[prjemian]

The workflow is failing, even when restarted. This error is reported:

AttributeError: 'FileNotFoundError' object has no attribute 'read'

Same is found when trying locally now (to create a custom conda environment to apply syntax checks, same as worflow). The problem seems to be:

definitions/environment.yml

Lines 8 to 9 in 493adbe

	- pip:
	- -r file:requirements.txt

[prjemian]

What started as a quick and simple change has escalated into this chain of issues to be resolved (in order): #950, #949, #946.

Closing this PR and deleting the branch to start over. Later. Placement in the TODO column of the project page has been adjusted.