ISD-2548 update README

[Thanhphan1147]

Update the charm’s README on GitHub to follow the template outlined in is-charms-template-repo.

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated
• The PR is tagged with appropriate label (urgent, trivial, complex)

[github-actions]

Test coverage for c24ab8a

Name                                       Stmts   Miss Branch BrPart  Cover   Missing
--------------------------------------------------------------------------------------
src/charm.py                                 171     12     16      3    91%   142-145, 152, 196, 395, 415-420
src/exception.py                               2      2      0      0     0%   6-10
src/resource_manager/gateway.py               77      4      8      0    95%   91, 154, 209-210
src/resource_manager/http_route.py            64      0      0      0   100%
src/resource_manager/permission.py            19      0      2      0   100%
src/resource_manager/resource_manager.py      43      4     10      4    85%   40, 100, 104, 122
src/resource_manager/secret.py                54      2      2      1    95%   65, 160
src/resource_manager/service.py               43      1      0      0    98%   122
src/state/base.py                             11      0      4      0   100%
src/state/config.py                           42      0      4      0   100%
src/state/exception.py                         2      0      0      0   100%
src/state/gateway.py                           8      0      0      0   100%
src/state/http_route.py                       29      0      2      0   100%
src/state/tls.py                              29      0      4      0   100%
src/state/validation.py                       31      2      2      0    94%   75-76
src/tls_relation.py                           78      5     10      4    90%   59, 97-103, 117, 129, 145->exit, 169->exit
--------------------------------------------------------------------------------------
TOTAL                                        703     32     64     12    94%
Coverage failure: total of 94 is less than fail-under=95

Static code analysis report

Run started:2024-11-09 01:17:23.074715

Test results:
  No issues identified.

Code scanned:
  Total lines of code: 2964
  Total lines skipped (#nosec): 0
  Total potential issues skipped due to specifically being disabled (e.g., #nosec BXXX): 0

Run metrics:
  Total issues (by severity):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
  Total issues (by confidence):
  	Undefined: 0
  	Low: 0
  	Medium: 0
  	High: 0
Files skipped (0):

[erinecon]

I'd prefer to remove jargon like "day N" whenever possible, so possibly rephrase the beginning of that sentence to read "This charm simplifies deployment and operations..."

[erinecon]

Are there developer docs we can point to here?

I think it would be good to also list the official webpage: https://gateway-api.sigs.k8s.io

[erinecon]

Are there any basic operations (e.g. actions) or integrations worth mentioning for this charm?

[erinecon]

I think it would be good to also include a link to Matrix in this list