Update project history timeline.

Add a few notable events which have occurred since the last update. Also minor change to make text look better when changing from light/dark mode.

docs/css/style.css

@@ -225,7 +225,6 @@ details .md-typeset__table {
 
 .timeline-date {
     font-family: "dcrdocs-code";
-    color: #596D81;
     white-space: nowrap;
     font-size: 14px !important;
     padding: 14px !important;
@@ -234,5 +233,4 @@ details .md-typeset__table {
 .timeline-event {
     font-size: 15px !important;
     padding: 14px !important;
-    color: #596D81;
 }

docs/getting-started/project-history.md

@@ -88,3 +88,9 @@ Politeia was launched with a git-based backend with censorship tokens for ensuri
 | December 28, 2021 {: .timeline-date}  | [First payment to contractors from the decentralized treasury (tspend)](https://dcrdata.decred.org/tx/f57f2f35abcfc58cb8d45da6315982610203c1335ee0d68b36240f22c24a557a) {: .timeline-event} |
 | January 24, 2022 {: .timeline-date}   | [Release of Decred software v1.7.0](https://github.com/decred/decred-binaries/releases/tag/v1.7.0) {: .timeline-event} |
 | April 10, 2022 {: .timeline-date}     | [Approval of DCP0007 (fix treasury bug), DCP0008 (explicit version upgrades), DCP0009  (automatic ticket revocations) & DCP0010 (Change PoW/PoS Subsidy Split)](https://voting.decred.org/) {: .timeline-event} |
+| May 8, 2022 {: .timeline-date}        | [PoS vote reward increased to 80%, PoW reward decreased to 10%](https://decred.org/news/2022-05-09-decred_shifts_to_majority_pos/) {: .timeline-event} |
+| December 15, 2022 {: .timeline-date}  | [Bison Relay launched](https://decred.org/news/2022-12-15-decred-launches-bison-relay/) {: .timeline-event} |
+| June 13, 2023 {: .timeline-date}      | [Release of Decred software v1.8.0](https://github.com/decred/decred-binaries/releases/tag/v1.8.0) {: .timeline-event} |
+| August 1, 2023 {: .timeline-date}     | [Approval of DCP00011 (Change PoW to BLAKE3 and ASERT) and DCP0012 (Change PoW/PoS Subsidy Split To 1/89)](https://voting.decred.org/) {: .timeline-event} |
+| May 8, 2023 {: .timeline-date}        | PoS vote reward increased to 89%, PoW reward decreased to 1%. PoW algorithm changed to BLAKE3 (CPU mining only) {: .timeline-event} |
+| September 6, 2023 {: .timeline-date}  | GPU mining for BLAKE3 started {: .timeline-event} |