Add promtail chart

[torstenwalter]

This adds the promtail chart from the loki repository to this repo.

It includes the existing history. You can verify it yourself by checking the history for individual files as in the example:

$ git log --oneline charts/promtail/Chart.yaml
7f491d0 adjust README to new chart repo
58aec3e helm chart: Fix broken logo (#2651)
0cd01e9 Update helm and jsonnet to new release (#2809)
51a57d2 Promtail: (and also fluent-bit) change the max batch size to 1MB  (#2710)
eafc9b0 [Promtail] enables configuring psp in helm chart (#2659)
03b944e updating images to 1.6.0 (#2504)
8b96ffd promtail: enable externalIPs support for syslog (#2490)
b5ba2ca Add emptyDir volume type to promtail PSP (#2379)
da9a22d Add projected and downwardAPI volume types to PodSecurityPolicy (#2355) (#2366)
ca6f2e0 helm: add annotations to service monitor (#2258)
2e793d7 Adds the ability to have a pull secrets for Promtail. (#2141)
e864f1e updating all the images to 1.5.0 release (#2100)
cc1bc31 Change image tag from 1.4.1 to 1.4.0 in Helm chart (#2015)
f0becad added extraCommandlineArgs in values file (#1981)
2f22bdb Reverting helm changes which were included in Cortex 1.0 vendor upgrade because it resulted in us pushing an unstable helm.
dfc0778 bumps helm to keepalive-master after cortex vendoring (#1937)
79234cb updating helm and ksonnet to 1.4.1 updating Fluent Bit to correct image
f403d40 [helm loki/promtail] make UpdateStrategy configurable (#1898)
b53037c updating helm and ksonnet for 1.4.0 release
0bd7c10 Add extraMount, extraVolumeMount to promtail helm chart for systemd-journal (#1871)
eabe9ae [promtail helm chart] - Expand promtail syslog svc to support values (#1731)
33350b2 fix promtail/templates/NOTES.txt to show correctly port-forward command (#1697)
23b3ca4 [promtail helm chart] Enable support for syslog service (#1617)
f7cf65c Promtail Helm Chart: Add support for extra environment variables (#1529)
bd6e080 added ability to configure kernel setting fs.inotify.max_user_instances through init container to resolve issue with too many open files (#1620)
43ca2e1 updating to 1.3.0 release
e9e3392 Allow extra command line args for external labels like hostname (#1530)
0d492c2 Helm: fix issue with config.clients (#1431)
53c4f6c v1.2.0: update helm and ksonnet (#1389)
3563f1c Updating version numbers for 1.1.0 release
7a639ab updating helm and ksonnet to version v1.0.0 (#1292)
727fdee Helm path update (#1061)
c776952 update versions to new release
92f3a94 Helm: Fix the reference error of loki/loki helm chart (#1056)
e4715c1 Helm chart: Allow additional scrape_configs to be added (#1134)
c6b0658 helm chart: Add missing operator to promtail (#967)
cf68f7c Add support for additional labels and scrapeTimeout for serviceMonitors
4fca8ec update  helm and ksonnet to 0.3.0
f4238a2 Reorder relabeling rules to prevent pod label from overwriting config defined labels
61c077f release: update ksonnet and helm charts to version v0.2.0
424f36e Helm: Be able to customize the Namespace (#830)
3b82ef3 Update chart version
81c54b7 updating versions for loki v0.1.0
481929f Added namespace to helm install notes (#617)
06ca1fb Helm: Allow custom pipeline stages (#580)
ddabd7a Support CRI 1.14+ directory change
8e67e52 Add scrape config for control plane static pods
99c53c6 Configurable Loki scheme in helm file, with optional basic auth (#494)
d3e45c9 Add a /ready endpoint to promtail
3cb048a Fix missing volume after refactor
e5ed45a Separate loki & promtail charts

Filtering the history was did a great trick on reducing the history size.

In addition to migrating the repositories the following things have been done:

• all linting errors in Markdown files have been resolved
• minor version of the charts has been increased
  The goal of this is to publish a newer version of the charts from this repo. I choose to increase the minor version so that it's possible to increase the patch version to deprecate the existing charts and point to the new location.
• READMEs was adjusted to take the new helm repository location into account.

Note:

• I disabled validation of maintainers as "Loki Maintainers" is not a valid GitHub username.
  Here one should decide if one explicitly want's to name all maintainers or refer to a github team which exists.
  Not sure if GitHub teams could be resolved, but we could at least use it in CODEOWNERS file.
• DCO check is failing as history was imported. We should ignore it for this PR.

Part-of: grafana/loki#2593

[slim-bean]

LGTM!