Bug in displaying pcd files with lowercase written type

[FrederikPlahl]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for main branch).

Describe the issue

The bug is a follow-up on the question #6924 I wrote earlier. As mentioned there, all points get located in the origin, when the pcd file is opened, but no error message gets raised. Other programs are able to open those pcd files without an issue.
I found that the problem lies within the header of the pcd file, where TYPE describes the type of the following data. In the case resulting in an error, it looks like this:

TYPE f f f f

If you change the lowercase letters to uppercase everything works:

TYPE F F F F

Steps to reproduce the bug

# This file produces an error. Notice the lowercase type. After changing to uppercase everything works fine.

VERSION .7
FIELDS x y z rgb
SIZE 4 4 4 4
TYPE f f f f
COUNT 1 1 1 1
WIDTH 213
HEIGHT 1
VIEWPOINT 0 0 0 1 0 0 0
POINTS 213
DATA ascii
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0.944 0.29474 0 4.2108e+06
0.98111 0.24247 0 4.2108e+06
0.93655 0.26143 0 4.2108e+06
0.91631 0.27442 0 4.2108e+06
0.81921 0.29315 0 4.2108e+06
0.90701 0.24109 0 4.2108e+06
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0.8102 0.29315 0 4.2108e+06
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Error message

No response

Expected behavior

As many other 3d viewers, open3d should accept a lowercase written type as well as an uppercase.

Open3D, Python and System information

- Operating system: Ubuntu 20.04
- Python version: Python 3.10.12
- Open3D version: 0.18.0+18a47ef
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: pip

Additional information

No response